Question

where引导状语从句和名词性从句在介词使用方面的问题

where引导状语从句，主句和从句中的不及物动词后面还需要加介词嘛，是I live where they live.还是I live in where they live in.
where引导名词性从句，从句中不及物动词后面还需要加介词嘛，是That is where their happiness springs from.还是That is where their happiness springs.
为什么？

Answer 1

应该说, I live where they live.
in 要去掉。
这句完整的说法是， I live in the place where they live.
I live in the place in which they live.
I live in the place which they live in.
后两种情形是需要用 in 的。第一种不能，因为 关系副词 where = in which.../ which...in
其次，That where their hapiness springs from. 没有错。
虽然 where 是 疑问副词或关系副词，通常where 是不能再与介词搭配，因为这会导致语义重复，即where 本身就含有对应的介词了：at/ in/ to /on ....
但是有个例外：from where 是没有错的。
例如： Where are you going?
不说； Where are you going to?
说： He went abroad to study.
不说： He went to abroad to study.
说： He returned from abroad.
不说： He returned abroad.