The possibility that a gas mixture may be above the upper flammable limit does not ensure that it is safe, as the

Answer and Explanation:

The possibility that a gas mixture may be above the upper flammable limit does not ensure that it is safe, as the gas vapor will become diluted and have its concentration decrease into flammable limit range IF EXPOSED TO AIR.

Therefore, being above the upper limit is not truly safe. If a gas mixture in a confined space is well above the upper flammable limit but ventilated or opened to an air source, there would be gas vapor dilution and drop in concentration of the gas mixture making it attain a flammable limit range.

it is b that is the answer.