I would absolutely go for the rat! Rats are smart, fast and have a good sense of smell and memory. If ten individuals have captured the train, the rat is small enough to pass into any space and find explosives if those are present. It will find a way to find all the terrorists and identify safe passages for people if such exist. It can also create a diversion for hostages to escape.
RE: Qurator's Mischievous Mondays | Special Animal Agent!