Which of the following is an inherited condition that, if untreated, leads to mental retardation?

A) egocentrism
B) narcolepsy
C) anorexia
D) phenylketonuria

Phenylketonuria

A genetic disorder that leads to the inability to metabolize the amino acid phenylalanine, requiring a strict diet to prevent intellectual disability and other health issues.

Egocentrism

The inability to differentiate between self and other, often leading to an individual perceiving, understanding, and interpreting the world primarily from their own perspective.

Narcolepsy

A chronic sleep disorder characterized by overwhelming daytime drowsiness and sudden attacks of sleep, often linked to abnormal REM sleep patterns.