When I try to understand ______ that prevents so many Americans from being happy as one might expect, it seemed to me that there are two causes.
| A．why it does | B．what it does | C．what it is | D．why it is |
No one helped me . I did it all myself .
| A．for | B．by | C．from | D．to |
To understand the grammar of the sentence，you must break it______ into parts．
| A．down | B．up | C．off | D．out |
The classroom is big enough, but we’ll have to move if we have more students.
| A．for the moment | B．on the moment | C．in a moment | D．for a moment |
—You know. Bob is a little slow ____ understanding, so…
— So I have to be patient ______ him.
| A．in ; with | B．on; with | C．in; to | D．at; for |
Mark was a student at this university from 1999 to 2003, ____ , he studied very hard and was made Chairman of the Students' Union.
| A．during which time | B．for which time | C．during whose time | D．by that time |