问题
选择题
_______sending emails, I've kept in touch with my American friend for many years.[ ]
A. In exchange for
B. On behalf of
C. In return for
D. By means of
答案
答案：D
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_______sending emails, I've kept in touch with my American friend for many years.[ ]
A. In exchange for
B. On behalf of
C. In return for
D. By means of
答案：D