单项选择题
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='21'
D、PublisherCode'21'