—_____ the population of the U.S.A. in 2005?
—It _____ about 296 million.
A.What is; is B.What was; was
C.How many is; was D.How many was; is
In summer milk will quickly go bad _____it is put into a fridge.
| A．though | B．unless | C．because | D．once |
I have heard a lot of good things about you _____ I came back from abroad.
| A．since | B．when | C．before | D． until |
—Why didn't you try your best to get on the bus?
—I tried to, but it had started moving ________ I could get on it.
| A．before | B．after | C．since | D．if |
—Did you call Jim back?
—I don't need to, ________ we'll have a meeting together tonight.
| A．though | B．unless | C．because | D．if |
In Britain, you must reach 18 ________ you want to drive a car.
| A．because | B．though | C．if | D．so |