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。将一根长24cm的筷子，置于底面直径为5cm，高为12cm的圆柱形水杯中（如图）．设筷子露在杯子外面的长为hcm，则h的取值范围是 _________ ．