句型转换。

1.  The boy is poor at English.  (改为同义句)

     The boy is ___________ ___________ English.

2.  I have a pain in my head.  (改为同义句)

     I have a  ___________.

3. His father went to Hong Kong five years ago.  (就画部分提问)

     ___________ ___________his  father   ___________  to Hong Kong?

4.  There is something wrong with his right leg.  (改为同义句)

    ___________ is wrong with his right leg.

简述数控机床维修的基本原则。