---Why didn’t youanswer my phone when I phoned you at about 11 p. m. yesterday?---I ________ andfailed to hear the phone.A.might havesleptB.must besleepingC.might besleepingD.must havebeen sleeping
网友回答
D解析虚拟语气。用must have done表示对情况的推测，排除BC。表示昨天11点时的正在进行的动作，应该用进行时态，排除A。