Todd is mentally retarded, sterile, and has small external genitalia, undescended testicles, and breast enlargement. His chromosome pattern is XXY

Since puberty, he has received hormone replacement therapy in order to maintain his secondary-sex characteristics. What sex-linked abnormality does Todd most likely have?
a. Klinefelter's syndrome
b. Down syndrome
c. Turner's syndrome
d. Fragile X syndrome

a