I had just started back for the house to change my clothes _____I heard my name called.

A. as           B. for              C. while            D. when

It is an interesting story and one can't put it down _____ one has finished reading it.

A. after            B. when             C. since            D. until

I have been keeping the portrait _____ I can see it every day, as it always reminds me of my childhood in Paris.

A. since        B. where        C. as           D. if

_____earth scientists understand how and why earthquakes happen, forecasts are usually inaccurate.

A. As           B. While        C. Because      D. If

Mr. Smith wanted to buy the house and he told me that ____the house cost，it would be worth it.

A. however      B. how much         C. whatever         D. what

I was so excited last night that it was a long time _____I got to sleep.

A. that         B. since            C. before           D. when

He finally won the general election because many of his promises were quite popular _____ the voters.

A. for          B. in           C. to                   D. with

During the class, Tom slipped out of the classroom ____the back door so as not to be found by the teacher.

A. across       B. in         C. by                 D. beside

She is _____a growing number of Chinese people who find it increasingly difficult to find time to read every day.

A. between      B. among     C. during          D. through

In the meantime, the question facing business is whether such research is    the cost.

    A. worth    B. worth of    C. worthy    D. worthwhile