【题目】—You look so tired. You________ late last night.
—Yes. I had to to do an important report and stayed up till I completed it.
A.should sleepB.must sleep
C.should have sleptD.must have slept
在线课程【答案】D
【解析】
考查情态动词。句意：—你看起来很累。你昨晚一定睡得很晚。 —是的。我必须完成一份重要的报告，而且要熬夜完成。根据回答“yes”以及后面的具体解释可知，第二个人肯定了第一个人的推测。表肯定推测，应用must。且根据last night可知，这是对过去的推测，应用must have done。should have done表虚拟，意为“本应该做某事”。故选D。