Early-onset Alzheimer's disease seems to be due to​

A) ​a genetic defect.
B) ​an accumulation of stressful life events.
C) ​an unusually high number of childhood illnesses.
D) ​an immune deficiency.

Early-Onset

Referring to the occurrence of a disease or condition at an earlier age than is typical or expected.

Genetic Defect

An abnormality in the genetic material (DNA) that may lead to diseases or malformations.

Alzheimer's Disease

A progressive neurological disorder that causes brain cells to degenerate and die, leading to severe memory loss and cognitive decline.