4. The North Island is famous for an area of hot springs, some of which throw hot water high into the air.
some of which throw hot water high into the air.是定语从句。some为部分of 后的which是整体，some 与of which可以交换位置。我们可以把这类定语从句归纳为部分与整体型的定语从句，即：部分+ of +which/who(先行词为人时关系代词用whom; 先行词为物时关系代词用which;)
There are 50 numbers in the club, most of whom are from the city.
=There are 50 numbers in the club, of whom most are from the city.
这个俱乐部里有50个成员，其中大多数来自城市。
I have 100 books, 30﹪ of which are on English.
= I have 100 books, of which 30﹪ are on English.
我有100本书，百分之30 是关于英语方面的书。
