There are no wordgames here, the phrasing is just a bit formulaic and thus may sound weird. However, the last question makes a subtle change in the order of its statements compared to previous ones to throw you off - Answer 1, 2 and 3 simply aren't supported logically.
1) We don't know what can be a bumper car, only that ambulances aren't. Maybe firetrucks are, do they save lives?
2) Again, we don't know for sure whether any of them are or aren't, it's just a possibility.
3) Again, there may be life savers besides ambulances. Those could be bumper cars.
4) This is the only one where we don't speculate. We know at least some life savers are ambulances and we're told that the ones that are, definitely aren't bumper cars.