在定语从句中 可以用介词加关系副词引导吗THANK YOU!关键是这个句子该怎样理解和分析！天呐！应该填什么

不能那样引导。但你说的这个题我见过，它属于介词后的宾语从句。

from where不是定语从句，是from（介词）后面加where引导的宾语从句再做状语，好复杂啊，呵呵 ，例如
He was standing at the top, from where he could see it clearly
补充：不是宾语从句，是状语啊，他站在顶部，从那里他可以看得更清楚

不能用介词+关系副词。 可以用介词+which=关系副词
介词+which可以代替when ，where，why等
I will never forget the days on which（when）we studied together.我永远忘不了我们一起学习的日子。
This is the town in which(where) Shakespeare was born.这就是莎士比亚出生的城镇。

（至于用什么介词需要看定语从句中动词或形容词的习惯搭配来确定）

可以、
例如 Frank's dream was to have his own shop in which to produce the workings of his own hands.

括号里填 in which

万万不行. 多数情况下,介词+关系代词=关系副词.
The school in which I studied is very famous now.
=The school where I studied is very famous now.
祝学习进步!