He had intended to do some physics homework during the play, but he soon _____ the play so much that he

forgot all about the homework. [ ]

A. busied himself enjoying 　　　　

B. involved himself to enjoy 　　

C. found himself enjoying　　　　　

D. convinced himself to enjoy

取下直流熔断器时，正确的操作为（），装上熔断器时相反。

A.先拉保护，后拉信号

B.先拉信号，后拉保护

C.先拉正极，后拉负极

D.先拉负极，后拉正极