What happens to make an embryo develop female sex organs?

The Y chromosome causes the gonads to release androgen, causing the Wolffian ducts to develop and the Müllerian ducts to deteriorate.

The Y chromosome causes the gonads to release estrogen, which causes the Müllerian ducts to develop and the Wolffian ducts to deteriorate.

The absence of the Y chromosome causes the gonads to develop estrogen-secreting ovaries, allowing the Müllerian ducts to develop and the Wolffian ducts to deteriorate.

The absence of the Y chromosome causes the gonads to release androgen, causing the Müllerian ducts to develop and the Wolffian ducts to deteriorate.