The flu is believed ________ by viruses that like to reproduce in the cells inside the human nose and throat．

A．causing

B．being caused

C．to be caused

D．to have caused

There are five pairs ________, but I'm at a loss which to buy．

A．to be chosen

B．to choose from

C．to choose

D．for choosing

Good ways of doing things mean saving time, and ________ it is important for us to find them．

A．otherwise

B．however

C．besides

D．therefore

It is difficult for any of us to eat better, exercise more, and sleep enough ________ we know we should．

A．because

B．even though

C．as if

D．unless

About 700 people crowded in Houston, waving flags and holding signs ________“Welcome Home, Astronauts!”when Discovery's astronauts arrived for a celebration．

A．to read

B．being read

C．reading

D．to be read

It was some time ________ we realized the truth．

A．when

B．until

C．since

D．before

－How about eight o'clock outside the cinema?

－That ________ me fine．

A．fits

B．meets

C．satisfies

D．suits

________, he talks a lot about his favorite singers after class．

A．A quiet student as he may be

B．Quiet student as he may be

C．Be a quiet student as he may

D．Quiet as he may be a student

________ as she is, she can look after her sick mother．

A．A child

B．To be a child

C．Being child

D．Child

Though ________ money, he managed to finish his college education．

A．lacking

B．lacked

C．was lacked

D．lacked of