It’s only when we have left school or college that we understand the greatness of our opportunity of education, which has gone for ever.请问which所引导的从句的先行词是?
—Why did you worry about me?I didn't take any risks.—Well,you ______ injured.A.must have beenB.could have beenC.should have beenD.would have been请教一下老师,这道题为什么选D?