— Must they clean and tidy the classroom now?
— No, they      . It       after school in the afternoon.

A．mustn’t; must clean	B．needn’t; must clean
C．mustn’t; need be cleaned	D．don’t have to; can be cleaned

科目 英语   题型 单选题   难度 较易

知识点： 情态动词的被动语态