这道题是选in which 还是where?希望高手解答~

题目

这道题是选in which 还是where?希望高手解答~
There is a delicate balance of nature _____ many square miles of ocean and vegetation and clean air are needed to maintain only a relatively few human beings.

答案

我觉得用that最为合适,where是做地点状语的,这里没有地点
其实in which也不合适,句子中什么成分都不缺,不知道这in用在哪里
that 可以引导同位语从句,后面的句子解释前面的 balance of nature