Cross-linking theory attributes the effects of aging to the _______.

A) influence of social factors
B) stiffening of body proteins
C) breakdown of immune functioning
D) reduction in nerve sensitivity and responsiveness

Cross-linking theory

A theory in biology and chemistry describing how chemical bonds form between different parts of a molecule or between molecules, affecting properties like elasticity in tissues.

Body proteins

Essential macromolecules that serve various functions in the body including as enzymes, antibodies, and structural components of tissues.