_____ to nuclear radiation, even for a short time, may produce variants (变异体) of genes in human bodies.
| A．Exposed | B．Being exposed |
| C．Having exposed | D．After being exposed |
David left word with my secretary ________ he would call on me in the afternoon.
| A．who | B．that | C．where | D．which |
Why do you turn off the light in the room? We are in total ______ now and I can’t see anything.
| A．silence | B．darkness | C．progress | D．charge |
You’re our manager, so ______ or not you’ll attend today’s meeting is very important.
| A．/ | B． what | C．if | D．whether |
I wonder why you failed so many of the questions. Only the first question was difficult, but the rest, I thought, ______ very easy.
| A．is | B．are |
C．was | D．were |
I will ______ Tom as soon as possible when I have enough money. I don’t want to be in debt for too long.
| A．give back | B．give up |
C．pay back | D．pay up |