We need to select an answer that is consistent with the given information:
- 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.

At present, there seems to be a discrepancy in the information: if toxic gases are releases in/near the plane, passengers must exit to get away from the gases. But if they exit the plane and escape the gases, why would they need the smoke hood?

We need to select an answer that resolves this seeming discrepancy: that hoods are needed even though passengers are required to exit the plane.

(A) Test evacuations showed that putting on the smoke hoods added considerably to the overall time it took passengers to leave the cabin.
- this would give us reason NOT to use the smoke hoods. This wouldn't give us reason to require them.

(B) Some airlines are willing to buy the smoke hoods even though they consider them to be prohibitively expensive.
- ok, but that doesn't explain WHY we need the hoods.

(C) Although the smoke hoods protect passengers from the toxic gases, they can do nothing to prevent the gases from igniting.
- this gives more reason to the that the hoods WON'T help. We need a reason that they WILL help in addition to exiting the plane.

(D) Some experienced flyers fail to pay attention to the safety instructions given on every commercial flight before takeoff.
- irrelevant. This would cause issues for both evacuations and smoke hoods.

(E) In many airplane accidents, passengers who were able to reach emergency exits were overcome by toxic gases before they could exit the airplane.
- Yes! This gives us a reason to believe that smoke hoods are necessary even though passengers are exiting the plane away from the gases. Correct.

The answer is E.