Water, which seems to be so simple and common, is ______ makes life possible.
| A．that | B．which | C．what | D．where |
— This apple pie is too sweet, don’t you think so?
— ____________. I think it’s just right, actually.
| A．I hope so | B．Not really |
| C．Sounds good | D．No wonder |
Not until all the fish died in the river ____________ how serious the pollution was.
| A．did the villagers realize |
| B．the villagers realize |
| C．the villagers did realize |
| D．didn’t the villagers realize |
If he ___________ my advice then, he would not be in trouble now.
| A．should take | B．took |
| C．could take | D．had taken |
It doesn’t matter ___________ you turn right or left at the crossing — both roads lead to the park.
| A．whether | B．how |
| C．if | D．when |
It was in the school __________ he had studied ___________ he began the important experiment.
| A．that; where | B．in which; which |
| C．where; that | D．where; in which |