求

- Do you have any plan this summer vacation, Mary?    

- Sure, I’ d like to be a volunteer and help to _________ the Central Park.    [ ]

A. put up            

B. call up              

C. clean up            

D. cheer up

—Do you like to wash the car?

—No, _____. [ ]

A. It's interesting.

B. It's funny.

C. It's exciting.

D. It's boring.

机器设备修理完，试车前要检查电源接得是否正确，并认真检查机器各部位，确认无误方可开车。

散剂的质量要求不包括( )

A．干燥
B．疏松
C．色泽一致
D．混合均匀
E．呈棕褐色

试述生前发育可分为哪几个阶段？