BookStore数据库中有出版社表Publisher(PublisherCode, Publisher, Telephone)在某SQL语句中，WHERE PublisherCode IN ('21', '31')子句等价于________。
A、PublisherCode= '21' AND PublisherCode='31' B、PublisherCode= '21' OR PublisherCode='31' C、PublisherCode<='31' AND PublisherCode>='21' D、PublisherCode<'31' AND PublisherCode>'21'