♥ You can cancel out C, storing flammable objects outside your house is very unsafe and should never happen.
♥ Cancel out D, depending on a fire, a fire extinguisher wouldn't clear the fire.
♥ B
and A are now left, A, yes A can be useful, but also if you were to be sleeping, how would you know the fire started?
♥ Which Is why I would go with B.
♥ B is very safe, and you can here the alarms beeping and immediately know whats going on rather then not knowing there is a fire by sleeping.