Some words are who and how.
The domestication of horses behavior changed quite a lot because before they were domesticated they were WILD horses. So they probably were aggressive animals. Considering how big horses are they definitely would have kicked you if you approached them. Since horses have been domesticated they act less hostile. They have also became smarter, they have a really strong fight or flight system.
(I don't know if this helped, but it took me awhile to find this information)
I think it is A) Reference
Well for starters cross out A) because everything doesn't have to be entertaining at the same time, cross out B) because its important to have evidence so people know its true, so its C) because showing evidence helps the audience know its correct.
