一題關係名詞where?

This is the place in which we met last night.
=This is the place where we met last night.
=This is the place that we met last night.
=This is the place which we met in last night.
看出其不同了吧!本題關鍵在介詞to，所以只能用that或to which 或which I went to

We can view the sentence as the joining of two clauses (each embeds a relative clause itself) by the conjunction "and" :
1. I often think of the school [關係代名詞] I went to.
2. I often think of the friends [關係代名詞] I made there. ("there" - the adverb refers to "the school")

** After joining, "the school" and "the friends" become the objects of the phrasal verb "think of", each of which is modified by a relative clause.

1. [關係代名詞] - can be "that" or omitted
The relative adverb "where" cannot be used, because of the presence of the preposition "to".
Otherwise, we can say: I often think of the school where I went. ("where" replaces "to which" or "that" .... "to")

2. [關係代名詞] - can be "whom" or "who" or "that" or omitted
The example opts to omit the relative pronoun.

通常，單純的指地方，關係代名詞用Where
The place where(單純的指地方) we had dinner last time was small and smelly.
I often think of the school where(單純的指地方) I went to is fun.
如指事情或超過單純的地方，關係代名詞用that
The food that(指後面的事情) they served there was really bad.
I often think of the school ____ I went to (指地方) and the friends I made there(交朋友是重點，是指事情).
因不是單純的指地方，故用that