Tim ___since he lost his job three weeks ago.

问题描述:

Tim ___since he lost his job three weeks ago.
A) had been unemployedB) was unemployedC) has been unemployed D) has unemployed

选 C 【since 是现在完成时的标志,be unemployed 失业的】为什么不选A哪?A 是过去完成时,但since 是现在完成时的标志,再如 :He has lived here since two years ago.