问题补充:
Each of the students, hoping to pass the exam, the book.
A. buying
B. having bought
C. should buy
D. to buy
答案:
A. buying
B. having bought
(答案→)C. should buy
D. to buy
解析:each of the students是句子主语,横线处为句子谓语,hoping to pass the exam是修饰句子主语的非限制性定语。