Which statement best describes the influence of heredity and environment on height?

• A. Heredity and environment contribute equally across all heights.
• B. Height is determined solely by environment.
• C. Environment is the primary influence, with heredity having minor role.
• D. Heredity is the primary influence, with environment affecting development only in severe situations.

Answer: (D)

Height is largely set by genetic factors, because many genes influence growth and the overall potential for stature. Studies of twins, including identical twins raised apart, show similar heights, highlighting a strong genetic influence on how tall someone can become. The environment matters too, especially during childhood: good nutrition, health, and absence of chronic illness help a child reach their genetic potential, while severe malnutrition or serious health problems can limit growth. Therefore, heredity is the primary influence, with the environment affecting development mainly in severe situations, which is why this statement best fits. The other ideas either overstate the role of the environment or understate the influence of genetics.