_____explanation is necessary.
| A．Farther | B．Further | C．Farthest | D．Furthest |
On entering the office, I found Mr. Thompson _____ at the desk and _____ something.
| A．seated； write | B．seated； writing | C．seat； write | D．seating； writing |
_____ how to express the idea in English, he turned to the dictionary.
| A．Does not know | B．Not knowing | C．Knowing not | D．Not to know |
You'd better not have the light _____ all day long.
| A．burning | B．burned | C．to burn | D．being burnt |
I had Helen's brother _____ the windows, but Helen had them _____ instead.
| A．to clean； cleaned | B．cleaned； cleaned | C．cleaning； cleaned | D．clean； cleaned |
Dick made it _____ to all his friends.
| A．to know | B．known | C．know | D．knowing |