题目

―Have you known Dr. Jackson for a long time?―Yes, since she________ the Chinese Society.A.has joined            B.joins                    C.had joined                D.joined 答案：D解析该句完整的句式是：I have known Dr. Jackson since she joined the Chinese Society. since后跟的时间状语从句要用一般过去时，表示自从过去某个时间发生的动作到现在以来有多长时间了。

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