—Look! A book is on the floor. Whose is it?
—It be Rick's. It has his name on it.
A. mustn't
B. can't
C. must
D. need
网友回答
A. mustn't
B. can't
(答案→)C. must
D. need
解析：考查情态动词的用法。mustn’t“禁止；不要”；can’t“不可能”；must“一定”；need“必要”。由下文句意“在上面有他的名字”可知，这本书一定是里克的。故选C。