限制性定语从句为何不需要in which

"How tall we are now is strongly influenced by the environment we grew up in," he said.

这个句子为何不是 the environment in which we grew up ?

请问老师们，这个句子环境后面的限制性定语从句为何不需要in which?

"How tall we are now is strongly influenced by the environment we grew up in," he said.

这个句子为何不是 the environment in which we grew up ?

请问老师们，这个句子环境后面的限制性定语从句为何不需要in which?

【答】假如 in which 放在定语从句开头，不可以省略作宾语的关系代词；假如介词放在定语从句末尾，作介词宾语的关系代词可以省略，也可以不省略。