Which of the following is the primary female sex organ?

The correct option is Ovaries.

To understand why ovaries are the primary female sex organs, let us break down the classification of the reproductive system:
1. Primary Sex Organs (Gonads): These are the organs that produce the gametes (sex cells) and secrete sex hormones. In females, the ovaries produce the female gametes called ova (eggs) and secrete hormones like estrogen and progesterone. In males, the testes are the primary sex organs.
2. Secondary (Accessory) Sex Organs: These structures do not produce gametes but are essential for the transportation, nourishment, and development of the gametes and the developing fetus. The uterus, cervix, fallopian tubes, and vagina are examples of secondary sex organs.
3. Mammary Glands: These are accessory glands of the female reproductive system that are involved in lactation (nourishing the newborn) but do not produce gametes or host fertilization/implantation.

Since the ovaries are responsible for producing the female gametes (ova) and the essential female sex hormones, they are classified as the primary female sex organs.