But they don't mean to cause any trouble,it is just that the

But they don't mean to cause any trouble,it is just that they...
But they don't mean to cause any trouble,it is just that they feel cut off from the older people's world,into ____ they have not yet been accepted.
a.which b.that c.the world d.it
选A 是非限定定语从句么?从语法上into which怎么解释
怎么翻译呢