However, at times this balance in nature is disturbed, ____ a number of possibly unforeseen effects.

A. lying in　　 B. calling in　　 C. taking in　　 D. resulting in

Michael ________ football regularly for many years when he was young.

A. was playing B. played　　　　　 C. has played 　　　 D. had played

______to sunlight for too much time will do harm to one’s skin.

A.Exposed 　　　 B.Having exposed　

C.Being exposed 　 D.After being exposed

______ with his office work, he had no time to attend to his sick daughter.

　 A. Keeping occupying　 B. Kept occupied　 C. Keeping occupy D. Keeping to occupy

Our boss is very ________； he doesn't call anyone by their first name.

A. formal　　 B. casual　 C. patient　 D. simple

I used to drink a lot of tea but these days I ＿＿coffee.
A. prefer              B. preferred                 C. have preferred         D. am preferring

This may sound silly to you，but if you think about it a little, it may not seem so strange ______.

　 A. after all　　 B. for all 　　 C. in all 　 　 D. above all

he mother did not know _____ to blame for the broken glass as it happened while she was out.
A who  B when  C how        D what

My parents have promised to come to see me before I _______  for Africa. 
 A. have left     B. leave    C. left      D. will leave 

It was reported that the passenger ship was sailing eastwards in the Atlantic Ocean ______ its captain and some passengers on board_______ something supposed to be a UFO flying overhead.

　　 A. while; caught sight of　　　　　　　　 B. when; caught sight of　

C. as; saw　　　　　　　　　　　　　　 D. since; caught a sight of