第13题: [单项选择]Professor Wilson has a speaking ______ for this weekend, so-he declined the invitation by his friends for dinner. A. employment B. enhancement C. engagement D. assignment 参考答案:C 答案解析:[解析] 名词辨义。这四个选项的词性都是名词,其中employment表示“雇用;使用”,enhancement是指“增进,增加”,engagement表示“约会;约定”,assignment表示“分