第21题: [单项选择]You'd better let me know as soon as there is a(n) ______ position in the branch office. A. empty B. vacuum C. hollow D. vacant 参考答案:D 答案解析:句意:分理处一有空缺你最好就告诉我。empty含义为“空无一物的”;vacuum是名词,含义为“真空,空虚”;hollow含义为“空洞的,中空的”,只有vacant与position搭配意为“空缺职位”。