Sex chromosomes of human female.

**The reasoning** Humans have 23 pairs of chromosomes — 22 pairs of autosomes (body chromosomes) and 1 pair of sex chromosomes that determine whether you're male or female. Females have **two X chromosomes (XX)**. Males have one X and one Y chromosome (XY). This is fundamental genetics: the combination you inherit from your parents determines your biological sex. Your mother (XX) can only give you an X chromosome. Your father (XY) gives either X (you become female) or Y (you become male). **Why the wrong options tempt you** - **A) XY** — This is the male pattern. Easy to confuse if you're rushing or didn't memorize which is which. - **C) YY** — Impossible in humans! You must get at least one X from your mother. YY can't exist naturally. - **D) XO** — This is Turner syndrome (a female with only one X chromosome) — it's a chromosomal abnormality, not the normal female pattern. **Quick takeaway** Remember: **"XX marks the woman"** — two X's make a female; XY makes a male. It's that simple!