Which Statement Is NOT True About Down Syndrome

Which statement is NOT true about Down syndrome?

A) It is caused by a third copy of chromosome 21.
B) Greatly increased incidence occurs with fathers over age 40.
C) It is usually associated with chromosomal nondisjunction in meiosis.
D) Characteristics include mental retardation and extra eyelid folds.
E) Affected individuals display mental retardation.