Have you ever wondered what makes living in this high buildings _____? (A)to be possible (B)possible 答案是(B) 想問(A)為何不行?

(A) 通常是用在"未來式"之中. 但是這原句 很明顯地是在講 現在 已經存在的事實 所以應該用 (B)

It is the idiomatic usage of the verb "make" when it means "cause to be, or to become".
pattern: subject + "make" + object of "make" + adjective
examples: make something difficult/easy/possible

The noun clause after "have you ever wondered" :
what (subject) makes (verb) living in this high building (object) possible (adjective as object complement)

= what makes it possible (for people) to live in this high building ....[dummy it for delayed object]