Mark Is Hyperactive, Often Flaps His Arms Wildly About, and Will

Multiple Choice

Mark is hyperactive, often flaps his arms wildly about, and will bang his head against a wall over and over for no apparent reason. He cannot relate to his peers very well and uses very bizarre language. His doctors have excluded him from a diagnosis of autism, because genetic testing revealed that damage to a chromosome can account for his symptoms. Mark probably has

A) fragile X syndrome.
B) PKU.
C) sickle-cell disease.
D) Down syndrome.