When a person first begins drinking alcohol, two drinks produce relaxation and drowsiness. After 1 year, four drinks are needed to achieve the same relaxed, drowsy state. Why does this change occur?
Correct Answer: B
Rationale: The correct answer is B: Tolerance develops. Tolerance occurs when the body adapts to repeated exposure to alcohol, requiring higher doses to achieve the same effect. Initially, two drinks were sufficient, but over time, the body adjusts, leading to the need for four drinks to achieve the same level of relaxation and drowsiness. This change is not due to the alcohol being less potent (A), antagonistic effects (C), or hypomagnesemia (D). Tolerance is a well-documented phenomenon in the context of alcohol consumption, explaining the increased amount needed to achieve the desired effect.