4.It was hard work， but they( )to it and got the job done.

1. Passage 20 Clifford Stoll ran a computer system in Berkelely， California. As a system administrator， he kept a close eye on the records. One day， Stoll found something strange in the payment record. There was a 75 cents mistake. One of the thousands of users had used the system for 75 worth of time and not paid for it. It might sound like very little money to worry about. But that 75 cents was the first clue Stoll had to a much bigger problem — that a hacker(黑客)had broken into Stoll‘s computer system. Who was it? Stoll spent the next year trying to find out. During that time the hacker used the system in Berkelely as a starting point to break into military computer systems all over the United States. Stoll had to keep track of the hacker‘s activities on the computer without the hacker‘s knowing someone was watching him. Stoll even made up huge files of false information so the hacker would have lots to read. When the hacker spent long time reading， the telephone company was able to trace the lines. After a year， the hacker was traced back to his computer — in Germany. He was later caught by the German police. The passage is mainly about( ).

5. Passage 19 Throughout her working life， a ship — like a motorcar — must be serviced regularly if she is to remain efficient. After a period at sea she must be overall checked and any necessary repairs must be made. There are also instances when a ship must be converted from being one kind of carrier to another. Most of today‘s oil， for example， is carried by huge super-tankers. The smaller tankers， many of which are still in good condition， can be converted into bulk carriers(散货船) for the transport of sugar， coal or ore. Conversion or repair work is carried out in a dry dock， a huge hole cut into the ground and lined with concrete. At one end are large gates separating the dock from the river or sea. When these gates are opened， water pours into the dock and fills it. A ship can then enter the dock， where it is carefully fastened in an upright position. When the ship is positioned inside the dock， the gates are closed and the water is pumped out. The vessel slowly settles on to wooden blocks. Wooden supporters are put in position between the ship and the sides of the dock to prevent her from rolling over. Great care is taken to make sure that the ship rests evenly on the keel(龙骨)blocks to prevent damage being done. As soon as the ship is firmly positioned， repair or conversion work can begin on her body or superstructure. According to the passage， how is a ship kept upright in a dry dock?

4. Passage 19 Throughout her working life， a ship — like a motorcar — must be serviced regularly if she is to remain efficient. After a period at sea she must be overall checked and any necessary repairs must be made. There are also instances when a ship must be converted from being one kind of carrier to another. Most of today‘s oil， for example， is carried by huge super-tankers. The smaller tankers， many of which are still in good condition， can be converted into bulk carriers(散货船) for the transport of sugar， coal or ore. Conversion or repair work is carried out in a dry dock， a huge hole cut into the ground and lined with concrete. At one end are large gates separating the dock from the river or sea. When these gates are opened， water pours into the dock and fills it. A ship can then enter the dock， where it is carefully fastened in an upright position. When the ship is positioned inside the dock， the gates are closed and the water is pumped out. The vessel slowly settles on to wooden blocks. Wooden supporters are put in position between the ship and the sides of the dock to prevent her from rolling over. Great care is taken to make sure that the ship rests evenly on the keel(龙骨)blocks to prevent damage being done. As soon as the ship is firmly positioned， repair or conversion work can begin on her body or superstructure. What do you think will happen to a dry dock when the repairs to a ship are completed?

3. Passage 19 Throughout her working life， a ship — like a motorcar — must be serviced regularly if she is to remain efficient. After a period at sea she must be overall checked and any necessary repairs must be made. There are also instances when a ship must be converted from being one kind of carrier to another. Most of today‘s oil， for example， is carried by huge super-tankers. The smaller tankers， many of which are still in good condition， can be converted into bulk carriers(散货船) for the transport of sugar， coal or ore. Conversion or repair work is carried out in a dry dock， a huge hole cut into the ground and lined with concrete. At one end are large gates separating the dock from the river or sea. When these gates are opened， water pours into the dock and fills it. A ship can then enter the dock， where it is carefully fastened in an upright position. When the ship is positioned inside the dock， the gates are closed and the water is pumped out. The vessel slowly settles on to wooden blocks. Wooden supporters are put in position between the ship and the sides of the dock to prevent her from rolling over. Great care is taken to make sure that the ship rests evenly on the keel(龙骨)blocks to prevent damage being done. As soon as the ship is firmly positioned， repair or conversion work can begin on her body or superstructure. We can infer that a dry dock( ).

2. Passage 19 Throughout her working life， a ship — like a motorcar — must be serviced regularly if she is to remain efficient. After a period at sea she must be overall checked and any necessary repairs must be made. There are also instances when a ship must be converted from being one kind of carrier to another. Most of today‘s oil， for example， is carried by huge super-tankers. The smaller tankers， many of which are still in good condition， can be converted into bulk carriers(散货船) for the transport of sugar， coal or ore. Conversion or repair work is carried out in a dry dock， a huge hole cut into the ground and lined with concrete. At one end are large gates separating the dock from the river or sea. When these gates are opened， water pours into the dock and fills it. A ship can then enter the dock， where it is carefully fastened in an upright position. When the ship is positioned inside the dock， the gates are closed and the water is pumped out. The vessel slowly settles on to wooden blocks. Wooden supporters are put in position between the ship and the sides of the dock to prevent her from rolling over. Great care is taken to make sure that the ship rests evenly on the keel(龙骨)blocks to prevent damage being done. As soon as the ship is firmly positioned， repair or conversion work can begin on her body or superstructure. Many smaller tankers have been converted into bulk carriers because( ).

1. Passage 19 Throughout her working life， a ship — like a motorcar — must be serviced regularly if she is to remain efficient. After a period at sea she must be overall checked and any necessary repairs must be made. There are also instances when a ship must be converted from being one kind of carrier to another. Most of today‘s oil， for example， is carried by huge super-tankers. The smaller tankers， many of which are still in good condition， can be converted into bulk carriers(散货船) for the transport of sugar， coal or ore. Conversion or repair work is carried out in a dry dock， a huge hole cut into the ground and lined with concrete. At one end are large gates separating the dock from the river or sea. When these gates are opened， water pours into the dock and fills it. A ship can then enter the dock， where it is carefully fastened in an upright position. When the ship is positioned inside the dock， the gates are closed and the water is pumped out. The vessel slowly settles on to wooden blocks. Wooden supporters are put in position between the ship and the sides of the dock to prevent her from rolling over. Great care is taken to make sure that the ship rests evenly on the keel(龙骨)blocks to prevent damage being done. As soon as the ship is firmly positioned， repair or conversion work can begin on her body or superstructure. According to the passage， in what way is a ship like motorcar?

5. Passage 18 Students can travel in the United States without spending too much money if they follow these suggestions. A travel agent can give you information on special economy fares for trains， buses and planes. Think about hiking or biking for a part of your trip， too. You‘ll not only save money， but you‘ll also see a lot more of the country. Some students may want to travel by car. Be sure to think about going with other students — many colleges have ―ride boards‖ that list when and where other students plan to travel. Many radio stations provide the same sort of service — they announce who‘s driving where， when， how many riders they will take and what the expenses will be. There are many inexpensive， older hotels near bus or train stations. Check your travel guide for names of the best. Many parts of the country also have youth hostels where young people can stay for only a few dollars a night. You don‘t have to eat in restaurants all the time， but we don‘t recommend a diet of candy and cola， either. You can usually get a healthy， cheap breakfast in a restaurant. If the weather is warm， you can buy food in supermarkets or at roadside stands and have a picnic for lunch. For dinner you can get the names of good， cheap restaurants from travel guides or friends. To save money， you can( ).

4. Passage 18 Students can travel in the United States without spending too much money if they follow these suggestions. A travel agent can give you information on special economy fares for trains， buses and planes. Think about hiking or biking for a part of your trip， too. You‘ll not only save money， but you‘ll also see a lot more of the country. Some students may want to travel by car. Be sure to think about going with other students — many colleges have ―ride boards‖ that list when and where other students plan to travel. Many radio stations provide the same sort of service — they announce who‘s driving where， when， how many riders they will take and what the expenses will be. There are many inexpensive， older hotels near bus or train stations. Check your travel guide for names of the best. Many parts of the country also have youth hostels where young people can stay for only a few dollars a night. You don‘t have to eat in restaurants all the time， but we don‘t recommend a diet of candy and cola， either. You can usually get a healthy， cheap breakfast in a restaurant. If the weather is warm， you can buy food in supermarkets or at roadside stands and have a picnic for lunch. For dinner you can get the names of good， cheap restaurants from travel guides or friends. According to the passage， staying at youth hostels is( ).

3. Passage 18 Students can travel in the United States without spending too much money if they follow these suggestions. A travel agent can give you information on special economy fares for trains， buses and planes. Think about hiking or biking for a part of your trip， too. You‘ll not only save money， but you‘ll also see a lot more of the country. Some students may want to travel by car. Be sure to think about going with other students — many colleges have ―ride boards‖ that list when and where other students plan to travel. Many radio stations provide the same sort of service — they announce who‘s driving where， when， how many riders they will take and what the expenses will be. There are many inexpensive， older hotels near bus or train stations. Check your travel guide for names of the best. Many parts of the country also have youth hostels where young people can stay for only a few dollars a night. You don‘t have to eat in restaurants all the time， but we don‘t recommend a diet of candy and cola， either. You can usually get a healthy， cheap breakfast in a restaurant. If the weather is warm， you can buy food in supermarkets or at roadside stands and have a picnic for lunch. For dinner you can get the names of good， cheap restaurants from travel guides or friends. If you want to share rides with others， you can get information( ).

2. Passage 18 Students can travel in the United States without spending too much money if they follow these suggestions. A travel agent can give you information on special economy fares for trains， buses and planes. Think about hiking or biking for a part of your trip， too. You‘ll not only save money， but you‘ll also see a lot more of the country. Some students may want to travel by car. Be sure to think about going with other students — many colleges have ―ride boards‖ that list when and where other students plan to travel. Many radio stations provide the same sort of service — they announce who‘s driving where， when， how many riders they will take and what the expenses will be. There are many inexpensive， older hotels near bus or train stations. Check your travel guide for names of the best. Many parts of the country also have youth hostels where young people can stay for only a few dollars a night. You don‘t have to eat in restaurants all the time， but we don‘t recommend a diet of candy and cola， either. You can usually get a healthy， cheap breakfast in a restaurant. If the weather is warm， you can buy food in supermarkets or at roadside stands and have a picnic for lunch. For dinner you can get the names of good， cheap restaurants from travel guides or friends. To see more of the country， you‘d better travel( ).