Every evening after dinner, if not______ from work, I will spend some time walking my dog.                                  

A. being tired     B. tiring        C. tired         D. to be tired

The missing boys were last seen____ near the river.

A.     playing  B. to be playing  C. play  D. to play

 Everyone knows that _______ is dangerous to play with fire, but _______ is difficult is to prevent children from playing with fire.

A. it, it                    B. what, what

C. it, what               D. what, it

He must be helping the old man to water the flowers,______ ?      

A. is he     B. isn’t he     C. must he     D. mustn’t he

When I worked as the general manager of the firm, I sometimes had _____ to visit London on business.

        A. opportunity       B. possibility       C. occasion      D. chance

He didn't _____ what I read because his mind was on something else.

         A. hold on    B. catch on    C. take in    D. get over

They decided to leave the waiter a big _____ because the food and service had been excellent.

         A. note         B. reward         C. tip         D. gift

I think we should let Maria go camping with her boyfriend. _____, she's a big girl now.

          A. Above all       B. After all       C. First of all      D. For all

I was out of town at the time, so I don’t know exactly how it _______. 

A. was happening        B. happened       C. happens       D. has happened

Many children，______ parents are away working in big cities，are taken good care of in the village.

A. their              B. whose         C. of them           D. with whom