题干
–Must I do my homework now ? ---No, you ______ . You may do it tonight.
A：can't
B：needn't
C：mustn't
答案(点此获取答案解析）
B
–Must I do my homework now ? ---No, you ______ . You may do it tonight.
A：can't
B：needn't
C：mustn't
的定义域为1，2，则函数
定义域为 （ ）