In terms of daily energy expenditure, which activity contributes the most?

The option indicating "Resting activity" is the primary contributor to daily energy expenditure is based on the understanding of basal metabolic rate (BMR). BMR represents the energy required for essential physiological functions while at rest, such as breathing, circulation, cell production, and maintaining body temperature. Since these functions occur continuously throughout the day, resting activity encompasses the largest portion of total daily energy expenditure compared to other activities.

Physical activity, while a significant factor in energy expenditure, typically contributes a smaller percentage relative to the energy burned at rest. The thermic effect of food, which involves energy expenditure related to the digestion, absorption, and metabolism of food, is also relatively minor in comparison, especially when considering a typical day’s total energy expenditure. Sleep activity, while providing energy conservation, does not require as much energy as resting awake since the body’s metabolic processes usually slow further during sleep.

Overall, resting activity, accounting for BMR, generally makes up a significant proportion—often around 60-75% of total daily energy expenditure for most individuals, thus highlighting why it is the correct choice in this context.