The biggest problem for most plants, which ___ just get up and run away when threatened, is that animals like to eat them.
| A．shan’t | B．can’t |
| C．needn’t | D．mustn’t |
Some students were late for class because they had been _________ by the heavy storm.
| A．kept | B．stopped | C．slowed | D．delayed |
________ you don’t lose heart, I’m sure you can pass the coming examination.
| A．Unless | B．If not | C．As long as | D．Although |
—How much of the foreign expert’s speech have you understood?
—Almost nothing. I wish I ________ harder at English.
| A．worked | B．had worked | C．would work | D．were working |
At the crossroads, you have to drive very ________ to avoid traffic accidents.
| A．quickly | B．cautiously | C．curiously | D．perfectly |
David has to admit the fact ________ he has fallen behind the others in his class.
| A．whether | B．that | C．why | D．when |