As there is less and less coal and oil, scientists are exploring new ways of making use of ____ energy, such as sunlight, wind and water for power and fuel.
| A．original | B．alternative | C．convenient | D．staple |
I tried to phone her, but even as I _____ she was leaving the building.
| A．phoned | B．would phone |
| C．had phoned | D．was phoning |
In fact, _______ one cause that leads to the problem.
| A．cattle is | B．cattle are |
| C．cattles are | D．the cattles are |
The students _______ busily when Miss Brown went to get a book she _______ in the office.
| A．had written, left | B．were writing, has left |
| C．had written, had left | D．were writing, had left |
Her father works as a ______ in a hotel and her mother a ______ in a private company.
| A．cooker, typewriter | B．cook, typist |
| C．cooker, typist | D．cook, typewriter |
. I think you must be mistaken about seeing him at the theatre； I’m sure he _____ abroad all week.
| A．is | B．was |
| C．has been | D．had been |