现在完成时的几种常见的句型转换。

现在完成时可以转化成一般过去时，还可以转化成“It is/has been +时间段+since从句(用一般过去时)”等句型。

e.g. Jim has been back for a month.吉姆已经回来一个月了。= Jim came back a month ago.吉姆一个月前就回来了

= It is/has been a month since Jim came back.自吉姆回来已经有一个月了。= A month has passed since Jim came back. I have kept the book for two days. = I borrowed the book two days ago.

= It is / has been two days since I borrowed the book. = Two days has passed since I borrowed the book.