Question

it's reported that two schools both of which are being built in my hometown will open为什么不是

为什么不是both of them

Answer 1

both of which are being built in my hometown 定语从句在这里是two schools的定语。所以必须有关系代词which.

Answer 2

which这里作为定语啊。指are being built in my hometown 的学校。