—What led to his success ?
—He succeed _____ working hard .
| A．to | B．in | C．through | D．by |
That old man ________to be more than a hundred years old, but he looked much younger than most of the ninety-year-olds.
| A．expressed | B．explained |
| C．stated | D．claimed |
Something must be done to stop cutting down trees. ________ all the trees are cut down, the valuable soil will be washed away by the heavy rain.
| A．Whether | B．Unless |
| C．Once | D．Until |
Mr. Black, as far as I know, is said _______ a book on the history of the Ming Dynasty, which turns out to be a bestseller.
| A．to write | B．to have written |
| C．to be writing | D．having written |
The contributions of some companies have ________ much improvement in the teaching and learning environment in this university.
| A．carried out | B．changed from |
| C．resulted in | D．succeeded in |
The company has offered me a job, _________ needs great care and technique．
| A．it | B．that | C．the one | D．one that |