【题目】----Dave didn’t respond ________any of my emails.
----Something _______have happened to him.
A. on; must B. with; could
C. for; could D. to; must
在线课程【答案】D
【解析】考查介词和情态动词。句意：--我的邮件戴芙一封也没回复。--他肯定有什么事情。Respond to回应；must have done肯定做过，表示对过去情况的肯定推测。选D。