—— Why? Tom, your shirt is so dirty!
—— Mum, I ＿＿＿＿＿ my storeroom downstairs。
| A．cleaned | B．have worked | C．was cleaning | D．have been cleaning |
We must take measures to protect endangered wildlife _______ it is too late.
| A．now that | B．as long as | C．unless | D．before |
Listen!, his family must be quarreling, _______?
| A．mustn’t it | B．aren’t they | C．isn’t it | D．needn’t they |
We read them ________; we remember them________.
| A．as young; as old | B．as younger; as older |
| C．when young; when old | D．when younger; when older |
Doctor Brown says that _______ what forceful arguments against cigarette harm there are, many people insist on smoking.
| A．though | B．however | C．no matter | D．even if |
The government has taken some measures to solve the shortage of electricity, but it may be some time _______ the situation improves.
| A．since | B．when | C．unless | D．before |