It will not be long _____man can harness the solar energy and make it serve mankind.
| A．since | B．before | C．when | D．after |
People have planted a lot of trees and grass in order to ____ wind and sand in the desert.
| A．hold down | B．hold up | C．hold back | D．hold out |
Read the passage and correct the mistakes, ______.．
| A．if not | B．if any | C．if ever | D．if never |
——Could I use your English dictionary for a few moments?
—— ________．I’m not using it myself.
| A．Come on | B．It depends | C．Go ahead | D．That’s great |
Whether ways will be found to stop pollution or not is just___________ worries the public.
| A．why | B．which | C．that | D．what |
—Have you seen Rose recently?
— No．It’s five years _____ I met her．
| A．since | B．after |
| C．when | D．before |