since 与 before 的区别?

Mr. Green has lived in China since I came here ? Mr. Green has lived in China before I came here ?第一个正确吗?before是不是也可以用于完成时态?请解释?

before引导的时间状语从句中常用一般现在时,主句用一般将来时。Since引导的时间状语从句中用一般过去时,主句用现在完成时或一般现在时(主语为 it 时)。 It will be five years before we meet again. It is five weeks since we came here.
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第1个回答  2014-12-07
第一个正确,自从我来到这儿他就生活在中国了 before可用于将来完成时,如I will have finished my homework before you come back.