MindTap Growth And Development Practice Test

Prenatal exposure to alcohol is the leading preventable cause of intellectual disability because alcohol consumed during pregnancy can cross the placenta and disrupt the developing brain, leading to fetal alcohol spectrum disorders that include cognitive impairments. This risk is avoidable by not drinking at any point during pregnancy, making it the most impactful preventable factor. The other options don’t fit as the main source: malnutrition in adulthood affects health later but not the early brain development that leads to intellectual disability; lack of physical activity influences general health rather than causing an intellectual disability; head injuries in adolescence can cause cognitive problems but do not account for the majority of intellectual disabilities that originate earlier in life.