BookStore数据库中有出版社表Publisher(PublisherCode,Publisher,Telephone)在某SQL语句中，WHEREPublisherCodeIN('21','31')子句等价于________。
A.PublisherCode='21'ANDPublisherCode='31'
B.PublisherCode='21'ORPublisherCode='31'
C.PublisherCode<='31'ANDPublisherCode>='21'
D.PublisherCode<'31'ANDPublisherCode>'21'
正确答案：B