单选题 23.  Employees like to think that they'll be promoted if they do an excellent job; however, most promotions are based on ______.
【正确答案】 C
【答案解析】 选项A错误,lengthen是动词。选项B和D都是形容词。选项C正确,longevity在这里的意思是“供职年限”。