The smoggy weather has made us realize ________ terrible problems we are faced with.
| A．how | B．what |
| C．that | D．which |
________ he found the idea interesting, it was too difficult to be of practical use.
| A．While | B．Once | C．If | D．Until |
As they were walking around, they noticed a man _______ against a tree.
| A．sit | B．to sit | C．sitting | D．sat |
Do some warming up exercise before sports. Or you _______ hurt yourself.
| A．must | B．need | C．should | D．may |
Teenagers ________ their sense of hearing because they always wear earphones.
| A．damage | B．are damaging |
| C．has damaged | D．will damage |
What the sick child needs most now ______ love.
| A．is | B．are | C．was | D．were |