是的，这是省略if的虚拟倒装: 在if引导的虚拟从句中，如果含有助动词had, should,were时，可以省略if, 将助动词提到主语前边来，形成倒装。 所以你给出的这句话Had he not been so busy ,he would have noticed the detective in the coner of the court-room =If he hadn't been so busy,he would have noticed the detective in the coner of the court-room. 其他的例子还有: If she had been given more information, she could have answered the questions.=Had she been given more information, she could have answered the questions. If it should rain tomorrow, we would not be able to have the sports meeting.=Should it rain tomorrow,we would not be able to have the sports meeting. Hope my answer can help you solve the problems ^_^