【题目】– Tom, it's too late. Our son ________ be back.
– Don't be anxious. I dare say he ________ have some extra work to do.
A.must，must
B.should ，should
C.should ，must
D.must ，should

【答案】C
【解析】考查情态动词。should "按理说，应该” must “肯定”。句意：---Tom，太晚了，我们儿子应该回来了。---别担心。我敢说他一定有些额外的工作要做。