问题
As we know, you won’t go back to the USA since you have established a research center hereBut how long _____ in America? —– For almost 10 years
A:did you study
B:have you studied
C:were you studying
D:have you been studying
B:have you studied
C:were you studying
D:have you been studying
正确答案是：
同类题型
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