You should make a careful plan ___ the experiment.
| A．before to do | B．before doing | C．after to do | D．after doing |
It doesn’t matter if they want to come to your party, ______?
| A．doesn’t | B．does it |
| C．don’t they | D．do they |
It was with the help of the local guide ______ the mountain climber was rescued.
| A．who | B．that | C．when | D．how |
—What’s all that noise about outside?
—Oh, I forgot to tell you. The road to the railway station ______.
| A．will be widened | B．is to be widened |
| C．has been widened | D．is being widened |
We human beings should be very careful with what we do with nature, _____power is beyond our understanding.
| A．that | B．which | C．whose | D．where |
Scientists are convinced ______ the positive effect of laughter ______ physical and mental health.
| A．of; at | B．by; in |
| C．of; on | D．on; at |