What would likely happen if you were exposed to a 100% methane atmosphere for more than 15 minutes?

Correct Answer: Option A — suffocate

Methane is a simple asphyxiant; while not inherently toxic, a 100% methane atmosphere contains zero oxygen. Exposure to such an environment for 15 minutes will lead to rapid oxygen deprivation, causing the victim to suffocate as the body's vital organs are starved of the oxygen required for survival.