Jet lag is getting out of one's normal __________ rhythm.

Answer: B — Circadian

Jet lag occurs when a person's internal body clock, or circadian rhythm, is disrupted due to traveling across different time zones. The circadian rhythm is a natural process that regulates the sleep-wake cycle and other physiological processes over a roughly 24-hour period. When traveling, particularly east or west, the external environment's time, such as light and darkness, becomes misaligned with the body's internal clock. This misalignment can lead to symptoms such as fatigue, difficulty concentrating, and sleep disturbances, which are characteristic of jet lag. Understanding this concept emphasizes the importance of aligning your daily schedule with the new time zone to help mitigate the effects of jet lag.