题目

Professor Smith and Professor Brown will _____ in giving the class lectures. 　　A. exchange       B. alter       C. shift       D. alternate   答案： D alternate vt./vi. 轮流，交替发生或出现；shift般动，移动(vt.);转移到，迁移(vi.);改变；exchange交换;exchange... for ... 用.......换......;alter(部分)修改。  

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