初中英语虚拟语气为什么这里aren`t不用weren't后面用will不用would’t?

couldn`t have done 不用于虚拟语气 么 Every body is ok,aren't they?为什么用aren't they而不用isn't he? in case 后面用不用虚拟语气? what a happy family,为什么回答用isn,t it 不用aren,t Aren't you lucky.为什么不用You are luck. everyone'having a good time 为什么用aren't they 不用 He will come here if he isn't busy tomorrow. 这里为什么不用 if he w 虚拟语气只用would不用had? 为什么用would不用will 为什么用will不用would weren't there aren't any books under the desk.中的any为什么不用some