题目

下图中四幅气温垂直分布图反映了一次雾霾天气的生消过程。读图，回答第18题。 a                  b                   c                  d 18..正确反映雾霾天气生消过程的是    A.a→b→c→d          B.d→a→b→c        C.c→d→a→b          D.b→c→d→a 答案：D—I was told to be here before eight.   —Oh, you _____.  I'm sorry for not telling you that we have changed the plan.  [     ]A. must     B. can't      C. may          D. needn't