（Even though) Sedat （has been studying) English for three years before he came （to the Uni
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(Even though) Sedat (has been studying) English for three years before he came (to the United States), It is still difficult for him (to express himself).
A．Even though
B．has been studying
C．to the United States
D．to express himself
更新中~-
正确答案：B
解析：把has been studying改成had been studying(过去完成时)，因为 study English这个动作发生在he came to the United States之前，came to是过去时，所以study English是“过去的过去”，应该用过去完成时，而不是现在完成时。