问题
选择题
It has been two years _________ he came to China.
A．since
B．after
C．before
D．till
答案
答案：A
本题考查的是since引导的时间状语从句，since引导的从句为一般过去时，其主句为现在完成时，故选答案为A
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It has been two years _________ he came to China.
A．since
B．after
C．before
D．till
答案：A
本题考查的是since引导的时间状语从句，since引导的从句为一般过去时，其主句为现在完成时，故选答案为A