Simon was _____ why many of his friends didn’t turn up at his birthday party.

A．limited            B．crashed           C．spotted           D．puzzled

Though I was tired out that evening, I _____ from falling asleep by the great pain in my knee.

A．was prevented     B．had prevented      C．has prevented      D．am prevented

See the model ship ____in the pool? That’s what my father made for me last weekend.

A．float             B．floating           C．floated            D．to float

Jack was in low spirits those days and his friends did all they could _____ him up.

A．cheer            B．cheering          C．cheered          D．to cheer

There is a peaceful and calm _____ in the country, quite different from that of a big city. 

A．climate           B．atmosphere        C．system            D．situation

It was almost midnight when a fire _____ in the neighborhood.

A．blocked out        B．turned out         C．broke out         D．died out

_____ life exists on any other planet in the solar system still remains a question.

A．Why             B．Whether          C．How              D．Where

Most of the evidence was destroyed in the fire. _____, it would be almost impossible to prove Jim guilty.

A．Anyhow           B．However          C．Besides           D．Thus

_____ you have worked out the first problem, you may go on to work on the second.

A．Even if            B．Unless            C．Now that          D．Though

As we all know, smoking ___________ people’s health.

A．is harmful to       B．do harm fo         C．does harmful to     D．harm