【正确答案】 D

【答案解析】[解析] 在省略if的虚拟条件句中，需用倒装结构。C句时态不对，应该是If he had worked harder，表示与过去事实相反。比如：Had you come earlier，you would have met him(= If you had come earlier，you would have met him．)(如果你回来早些，你就看见他了。)