by the time都有什么意思、用什么时态?
问题描述：
by the time都有什么意思、用什么时态?
答
举例说明 可用于过去完成时和将来完成时
1.I had finished the work by the time he came back
2.We will have finished the work by the time he comes back为什么不能用现在完成时 by the time不就是 到现在为止的意思吗