I.S.題-electricity(急!急!) 6

這份I.S.功課後日要交了,希望各位幫我解答呢的題目,THX!! ^_^

safety in using electricity:

7. A circuit __________ works like a fuse,but if can be turned on again easily after switching 'off '.
8.Appliances which are doubly __________ should not need to be earthed.