15. Not until father came in ______ to prepare my lessons.
| A．I began | B．did I begin | C．I had begun | D．had I begun |
American English has changed ________ time．There are several reasons ________ this.
| A．over; for | B．for; with | C．in; of | D．during; about |
---What do you think of my article, professor?
---The former part is well written but _____ is just so so.
| A．the later | B．the last part | C．latest | D．the latter |
He was told that it would be at least three more months ______ he could recover and return to work.
| A．when | B．before | C．since | D．that |
To their surprise, they found the lecture given by the famous professor easy ______.
| A．to be understood | B．to understand | C．understanding | D．understood |
It was the first time ________ I ________ face to face with a thunder storm.
| A．when / had come | B．that / have come | C．when / came | D．that / had come |