31.I knocked on his door but nobody came to answer it.

45. The traffic jams during morning and afternoon rush hours are a headache in big cities now.

46. Apples here like water and sunshine.

50. Do you have access to the Internet?

63. He has taught English in this university ever since he moved to this city.

17. Have you seen Tom recently?

52. There is a large amount of energy wasted due to friction(摩擦).

43. Who can help me clean the room?

28. Most students feel satisfied with the progress they’ve made.

66. If you decided to learn a new language, you would have to devote all your efforts to it.