第15题: [单项选择]Professor Smith and Professor Brown will ______ in presenting the series of lectures on American literature. A. alter B. alternate C. substitute D. exchange 参考答案:B 答案解析:[考点] 考查动词词义辨析。 alter意为“修改,改变”;substitute意为“替代”,常与for搭配;exchange意为“交换,互换”,均不合句意。alternate意为“交替,轮