C where
where 带出的是地点状语从句.
where前面“trees grow well”其实在结构上已经是一个完整的句子,但是意思不完整.“there is enough water”也是结构完整的句子,然而怎样衔接呢?那就是“在那些（where）有足够水分的地方”,树木生长得很好.
像那个谚语也是 Where there's a will,there's a way.（有志者事竟成）
there's a will和there's a way都是结构完整的句子,where带出的是地方,因此前面那部分实质上是一个从句.句子的直译是“哪里有意志,哪里便有出路”.
in which 前面要加名词
I often visit the museum in which there are a lot of cultural relics.
此处in which 等于 where.
一楼答案是错的.
也请楼上不要抄我的答案!