I would go with B, but I don't really like the idea of shooting dinosaurs
B for me, as you can probably guess. not A, because, as Doc said, what're the chances of finding something that could help you stop a T. Rex in a normal building? and C is lunacy, because then, it can eat you, step on you, or just plain ram you and keep going after your friends, achieving nothing for you or your friends. you would be dying for nothing...
as for why i preffer B, Personally, i say that if it's harmful to you, and is actively targeting you or your friends as prey, you stop it at all costs. dont care what it feels if it's the one attacking you or your friends. i mean, if animals were to follow the same things that HF follows as far as opinions and ideas, then Trikes and Ankys wouldn't fight back when a Rex charged at them, or, a modern day example, Buffalo wouldn't defend themselves from Lions.