哈利波特原著里的一句话的时态疑问？

Question

Mr. Dursley always sat with his back to the window in his office on the
ninth floor. If he hadn’t, he might have found it harder to concentrate
on drills that morning.
为什么If he hadn't，之后用的是现在完成时而不是过去时

Answer 1

这是过去时的虚拟语气，表示与过去事实相反。所以用的是“hadn't”和“have found”。如果是现在时的虚拟语气，就用“If he didn't”了