By the time you arrive home ,I______,so please not make any noise when you come in?

题目

By the time you arrive home ,I______,so please not make any noise when you come in?
为什么是填shall be sleeping而不是shall have been sleeping?讲的详细点.

答案

用shall have been 的话是说sleep这个动作在主句动作之前已经持续了一段时间 是强调持续的 而句意强调的是回去的是候正在睡 即将来进行时 才能表达准确