Dr. Thomas has found that William, her patient, has a defect in a gene on the X chromosome of his 23rd pair, which has therefore resulted in a deficiency of a protein needed for William’s brain...

Dr. Thomas has found that William, her patient, has a defect in a gene on the X chromosome of his 23rd pair, which has therefore resulted in a deficiency of a protein needed for William’s brain development. William most likely suffers from

a. Down syndrome.

b. cretinism.

c. fragile X syndrome.

d. fetal alcohol syndrome.