Which option correctly pairs FL300, FL350, and FL400 with their Time of Useful Consciousness from longest to shortest?

• A. FL300 — 1-3 minutes; FL350 — 30-60 seconds; FL400 — 15-20 seconds
• B. FL300 — 15-20 seconds; FL350 — 1-3 minutes; FL400 — 30-60 seconds
• C. FL300 — 30-60 seconds; FL350 — 15-20 seconds; FL400 — 1-3 minutes
• D. FL300 — 5-10 minutes; FL350 — 1-3 minutes; FL400 — 30-60 seconds

Answer: (A)

Time of Useful Consciousness decreases as altitude rises because the body receives less oxygen the higher you go. Without sufficient oxygen, the brain and body lose function quickly, so you become unconscious sooner at higher altitudes.

So, the pairing that places the longest usable time at the lower altitude and the shortest at the highest matches the real effect of hypoxia: FL300 around 1–3 minutes, FL350 about 30–60 seconds, and FL400 roughly 15–20 seconds. These are approximate values and can vary by individual and activity, but the trend is clear: more altitude means less time before loss of consciousness.