Sex Determination via Chromosomes

Steps:

• Egg cells from the mother always carry an X chromosome.
• Sperm cells from the father carry either X or Y.
• A baby boy has XY chromosomes in the zygote.
• For XY, the egg provides X and sperm provides Y.

Why C is correct:

• It matches the biological process: maternal X combines with paternal Y to form XY zygote, defining male sex.

Why the others are wrong:

• A: XX zygote produces a girl, not a boy.
• B: Eggs never carry Y; only sperm do.
• D: YY zygote is not viable in humans.

Final answer: C