题目内容
Mary dropped in ____ Mr Smith, but he wasn' t at home, so she went to drop in ____ Mr Smith's office.
A. on, on B. at, at C. on. at D. at. on
C
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题目内容
Mary dropped in ____ Mr Smith, but he wasn' t at home, so she went to drop in ____ Mr Smith's office.
A. on, on B. at, at C. on. at D. at. on
C