A. They improved the pipes that were attached to the bottom.

B. They added a knob on the chain to pull more easily.

C. They improved the flush system to make it less water-consuming.

D. They improved the collection bowl to make it more sanitary.

A. Queen Elizabeth I.

B. Sir John Harrington

C. Thomas Crapper.

D. Queen＇ Elizabeth I＇s godmother.

A. It was difficult to pull the knob on a chain to release water from the bowl.

B. It was very difficult to put water into the bowl.

C. The basin had to be emptied and cleaned constantly.

D. Removing the waste was highly water-consuming.

A. The person who invented the toilet.

B. The significance of the toilet in our life.

C. The invention of the toilet.

D. The development of the toilet.