Recently, I'm quite confused about the usage of the first(second,third……)/next/last/only.
He was the first ____ the school in that area.
(A)to open (B) opening
The answer is (A).
But,I remember the first(second,third……)/next/last/only can be used with the relative pronoun "that".
For example,he was the first person "that" opened the school in that area.
Also,I remember relative pronoun can be deleted with the verb it brings turning into ving or vpp.
Therefore,in my mind,the sentence"He was the first opening the school in that area" can make sense.
So,what do you think?and why？or is it just an idiom？