给水管网最常出现的问题是（）。

A.变形

B.腐蚀

C.断裂

D.结垢

按要求完成下列句子

小题1:You should do your homework by yourself.(否定句)

You           do your homework by yourself.

小题2:He has found nothing in the room .(改为一般疑问句)

          He found        in the room?

小题3:I’d like to show Tom the modle plane .( 变为同义句)

I’d like to           the modle plane           Tom.

小题4:She started learning English last year .(就划线部分提问)

                       she          to learning English ?

小题5:She has got a notebook .(就划线部分提问)

                  she got.