问题
选择题
—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
答案
答案：C
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。