28．In December of 2015, the Second World Internet Conference was held in Wuzhen, ______ theme is to ensure peace and security in cyberspace.
A
whose
B
which
C
when
D
where
句子意思是，2015年12月份，第二届世界互联网大会在温州举行，它的主题是维护网络安全和稳定。关系词和theme之间有从属关系，所以选whose。
考查定语从句的引导词。
误选B。