"Most of"or "Majority of" ?

Please look at this question. "Zoo is one of the few major zoos in the world to have the ____ its animals in "cageless" open-air exhibits. (1)most of (2) almost (c)majority of (d) almost all of Its correct answer is (c)majority of. What I want to know is for the other things. (1) Does "almost" have a function of a pronoun ? In my dictionary, it's described only as an adverb,but I think I have seen it as a pronoun from before. Could you let me know it clear ? (2) It has to be written like this. most of the animals(o), most of its animals(x), most its animals(x), its most animals(o) almost all of the animals(o), almost all of its animals(x), almost all its animals(x), its almost all animals(o) (3) I'm not sure, but if...