I borrowed the book three weeks ago.同义句转换 I _ _ the book since three weeks ago.I borrowed the book three weeks ago.同义句转换 I _ _ the book since three weeks ago.现在完成时since和for什么的弄不懂 have+v(pp) have什么时候

Question

I borrowed the book three weeks ago.同义句转换 I _ _ the book since three weeks ago.
I borrowed the book three weeks ago.
同义句转换 I _ _ the book since three weeks ago.
现在完成时since和for什么的弄不懂 have+v(pp) have什么时候用had

Answer 1

have kept
现在完成时的since 后加 点时间
for 加 段时间
比如：I haven't seen you since we graduated.
I haven't seen you for 5 years.
有一个过去时间,在描述在这个时间点之前发生的动作,用had done
I had done my work before I left the office.