问题描述：
Robert is said ______ abroad ,but I don’t know what country he studying in .
A .to have studied B .to study C .to be studying D .to have been studying
选择哪个啊?
been 怎么使用?
A .to have studied B .to study C .to be studying D .to have been studying
选择哪个啊?
been 怎么使用?
问题解答：
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