In Beijing July and August are the months( )it rains very oftenAwhere Bthat Cwho Dwhen选哪个为什么
问题描述：
In Beijing July and August are the months( )it rains very oftenAwhere Bthat Cwho Dwhen选哪个为什么
答
这事一个时间状语从句,前面先行词是month,关系代词用when
整句的意思是北京的七八月份经常下雨.