单片机89C51的XTAL1和XTAL2引脚是（）引脚

A、外接定时器

B、外接串行口

C、外接中断

D、外接晶振

小题1:You may hurt yourself if you __________ (not be) careful.

小题2:Nobody knows what ______________ (happen) in 100 years.

小题3:When I was very young, I ________ (can  solve ) some problems by myself.

小题4:Alice, ________ (listen) to your teacher carefully.

小题5:You must spend as much time as you can_______ (read) English.

小题6:I’m looking forward to _________ (receive)my mother’s letter.

小题7:My mother and father_______ (visit) her grandparents next Sunday, aren’t they?

小题8:Now Tom with his parents   ________(plan) to visit Qingdao this summer.

小题9:It’s important _________ (learn) English well if you want to find a good job.

小题10:Can they __________ (finish) the work by themselves?