Mary is pregnant with her first child and has recently had genetic testing to determine whether her baby-to-be is growing normally. Among other things, her test results indicate that the twenty-third chromosome pair of her fetus includes one X chromosome and one Y chromosome. This means that:
a. Mary is expecting a girl.
b. Mary is expecting a boy.
c. Mary’s baby will have Down syndrome.
d. Mary’s baby has a 50-50 chance of having Klinefelter syndrome.

Sex determination in human follows the XX-XY mechanism wherein the human males have one copy of X and one copy of Y chromosomes as their sex chromosome. So, the human males have a total of 22 pairs of autosomes and one copy of each X and Y chromosomes as the 23rd pair.

The human females have 22 pairs of autosomes and one pair of X chromosomes as the 23rd pair.

If the genetic testing shows the presence of one copy of each X and Y chromosomes in the 23rd pair of chromosome in the fetus, the fetus is going to develop into a baby body.