答案：D

题目分析：句意：如果他赶上了早班火车，开会就不会迟到了。主句的谓语动词是would not have been ，说明与过去事实相反，从句则可以用if he had caught the morning train, 当if从句中有were、had或者should 时，在可以省略if，把were、had或者should放在句首构成倒装句形式。本句中含有had，所以不用if时，就变成了 Had he caught the morning train。所以选D。