Which of the following is a characteristic of biological aging?

The characteristic of biological aging that is reflected in the correct answer involves physical signs of aging. As individuals age biologically, they often experience observable changes in their bodies. These may include wrinkles, gray hair, decreased skin elasticity, and changes in body composition. These physical manifestations are a direct result of the natural aging process and can be influenced by genetic, environmental, and lifestyle factors.

The other options present characteristics that do not align with biological aging. Increased energy levels and enhanced cognitive functioning are typically associated with youth and peak physical condition, and these tend to decline with age. Similarly, an improved immune response is not characteristic of aging; rather, immune function generally weakens as people grow older, making them more susceptible to illness. Understanding these distinctions helps clarify why physical signs of aging are a key indicator of biological aging.