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.

【正确答案】 A

【答案解析】句意：怀特先生在一家化学制品进出口公司工作。但在休假期间，他一直在工业博览会干活。on leave休假。on duty值班，上班。on patrol在巡逻中。on guard在岗，警惕。