—You’re coughing badly，Martin. Why not give up smoking?
—Give up smoking？Easier said than done，Amy. Once you ______ the habit of smoking，it is very hard for you to ______.
| A．keep up; break it away | B．take up; drop it out |
| C．pick up; get rid of it | D．build up; do away with it |
From space, the earth looks blue. This is __________ about seventy-one percent of its surface is covered by water.
| A．why | B．how |
| C．because | D．whether |
It is not their interest but the need of the market __________ influences students' choices of college majors.
| A．that | B．which |
| C．what | D．who |
To her joy, Delia earned first the trust of her students and then __________ of her colleagues.
| A．that | B．one |
| C．ones | D．those |
It's time I __________ home. My mother should be waiting for me for dinner now.
| A．return | B．must return |
| C．returned | D．will return |
He is a foreigner and he is not accustomed __________ like that while he is in China.
| A．treating | B．to be treated |
| C．to being treated | D．to treat |