根据首字母填空。

1.  Sometimes I have a sore left  f_______.  I can't put on my shoe.

2.  The boy's _______ are very long:  He is good at the high jump,

3.  This morning my _______ ached, so I can't read more books.

4.  Don't talk with your m_______ full.

5.  An elephant has a long _______  

6.  You s_______ copy others' homework.

 7.  About three weeks a_______ his grandfather died.

简述建筑电气安装工程中的预检主要内容是什么？