Will's already back from the charity walk,______?

问题描述:

Will's already back from the charity walk,______?
——_______,Now he's talking a rest in the next room;
isn't he;Yes 请问为什么不能用has't he;Yes

因为前面的‘s只能是is的省略形式,is back就对,而要是理解成has 的话要用has been back,所以后面的反义疑问句只能用is,不能用has