Dr.Pierce examines a 10-year-old who has mental retardation,motor retardation,distinctive facial features,and an extra 21^st chromosome.Given this information,Dr.Pierce's diagnosis would most likely be

A) PKU.
B) XYY syndrome.
C) Down syndrome.
D) anencephaly.

Extra Chromosome

An abnormal condition where an individual has more than the usual number of chromosomes, leading to genetic disorders.

Mental Retardation

This term, now considered outdated and offensive, was formerly used to describe developmental delays in intellectual functioning and adaptive behavior. The more accepted term is "intellectual disability."

Motor Retardation

A delay or slowness in the development or use of the motor skills that significantly interferes with daily living.