—How did your mathematics exam go？
—I thought I ，but in fact I fell behind in the class.A.should have been the top 10B.could have been the top 10C.may have been the top 10D.need have been the top 10
网友回答
B解析考查虚拟语气。句意：你的数学考试怎么样？——我认为我能进前十名，但是实际上我在班里名落孙山。表示对过去事情的假设，意思是本来能够做某事而没有做，用“could+have+done”，故选B。