OG10-132 逃生题求助

132. Passengers must exit airplanes swiftly after accidents, since gases released following accidents are toxic to humans and often explode soon after being released. In order to prevent passenger deaths from gas inhalation, safety officials recommend that passengers be provided with smoke hoods that prevent inhalation of the gases.

Which of the following, if true, constitutes the strongest reason not to require implementation of the safety officials' recommendation?
(A) Test evacuations showed that putting on the smoke hoods added considerably to the overall time it took passengers to leave the cabin.
(B) Some airlines are unwilling to buy the smoke hoods because they consider them to be prohibitively expensive.
(C) Although the smoke hoods protect passengers from the toxic gases, they can do nothing to prevent the gases from igniting.
(D) Some experienced flyers fail to pay attention to the safety instructions given on every commercial flight before takeoff.
(E) In many airplane accidents, passengers who were able to reach emergency exits were overcome by toxic gases before they could exit the airplane.

我知道A是对的，为什么C不对呢？
不能防止气体燃烧不也是口罩的缺点之一吗？

求大牛解释！！