单选题 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

【正确答案】 B
【答案解析】[解析] 因叙述的是过去发生的动作，所以从句谓语动词要用表示过去的虚拟结构。