Dr. Bethune worked hard as if he （）       .

题目解析 题目：Dr. Bethune worked hard as if he （）. A.never had felt tired B.had never felt tired C.never felt tired D.was tired never 答案：B 解析：这是一个虚拟语气的用法。"as if"引导的从句表示虚拟条件，表示与过去事实相反的假设情况。根据虚拟条件句的规则，当从句表示与过去事实相反的情况时，主句用过去完成时。因此，正确答案是B选项："had never felt tired"。