In time of serious accidents, ________ we know some basic things about first aid, we can save lives.
| A．whether | B．until | C．if | D．unless |
.Wait till you are more ______. It’s better to be sure than sorry.
| A．inspired | B．satisfied | C．calm | D．certain |
.She will tell us why she feels so strongly that each of us has a role ______ in making the earth a better place to live.
| A．to have played | B．to play | C．to be played | D．to be playing |
.He suddenly saw what looked like a snake in the darkness. For an instant his heart seemed to stop ______.
| A．to beat | B．beating | C．beaten | D．being beaten |
I can think of many cases ______ students obviously knew a lot of English words and expressions but couldn't write a good essay.
| A．why | B．which | C．as | D．where |
---I'm sorry I stepped outside for a smoke. I was very tired.
---There is no ______ for this while you are on duty.
| A．reason | B．excuse | C．cause | D．explanation |