CPL Human Factors · Mock exam

The 'circadian low' — the period of greatest physiological drowsiness — typically occurs:

• A.At sunset only, when the transition from daytime to night-time light triggers melatonin release
• B.At midday, when solar radiation is strongest and body temperature peaks after the morning rise
• C.In the early hours of the morning (roughly 0200–0600) and, to a lesser degree, in the early afternoon
• D.Never — the human body maintains a constant alertness level throughout the 24-hour cycle