单选题 Mr. White works for a chemicals import and export company, but he has been working for this industrial fair, while he is ______ from that company.
A. on leave B. on duty C. on patrol D. on guard

【正确答案】 A
【答案解析】[解析] 介词短语辨析
怀特先生供职于一家进出口公司，不过，休假期间他还为这次工业展会做事。介词短语on leave意为“休假”符合题意。