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 |
to sunlight for too much time will do harm to one’s skin.
| A．Being exposed | B．Exposed |
| C．Having exposed | D．After being exposed |
They appearedme, so I had to explain to them.
| A．misunderstanding | B．misunderstood |
| C．to be misunderstood | D．to have misunderstood |
If China’s space technology has achievedbreakthrough in this field, it really is
amazing wonder.
| A．the; an | B．a; an | C．不填; the | D．a; 不填 |
All passengers ____, please fasten your seat belts and remain seated ____the plane is landing．
| A．on board; until | B．abroad; since | C．on the board; before | D．aboard; when |
He ____ busy then; otherwise, I believe, he would have given you a hand．
| A．had been | B．were | C．must be | D．was |