单选题 If our budget for office supplies ______, all new requests for them will have to be approved on a case-by-case basis.
A. is exhausting
B. are exhausting
C. is exhausted
D. will be exhausted

【正确答案】 C

【答案解析】高级问题空格内应填入动词的单数形式。以ex-开头的动词是及物动词。没有宾语则应使用被动语态。也就是选择C或D选项。最后，要掌握时间、条件状语从句的用法。
[高频词语] budget 预算 office supplies 办公用品 exhausted 耗尽的 on a case-by-case basis 在个案的基础上