The decline in _________in middle adulthood is largely attributable to the loss of muscle tissue and the corresponding increase in fatty tissue.

Question

The decline in _________in middle adulthood is largely attributable to the loss of muscle tissue and the corresponding increase in fatty tissue. ​

Quizplus · Accepted Answer

Resting metabolic rate declines in middle adulthood due to the loss of muscle tissue and an increase in fatty tissue, which leads to a decrease in overall body composition. Retaining muscle mass through exercise and a healthy diet can help slow down this decline. 
Option A (reaction time) declines with age but it is not specifically related to loss of muscle tissue. 
Option C (fluid intelligence) and D (crystallized intelligence) may also decline with age, but the reasons are related to cognitive processes rather than physiological changes in the body.

The Decline in _________In Middle Adulthood Is Largely Attributable to the Loss