Therefore option C, Oestrogen, is factually consistent with the stem, the marked correct index, and the explanation.✅ Correct Answer: C — Oestrogen Oestrogen (Estrogen) is the primary female sex hormone produced mainly by the ovaries. It regulates the menstrual cycle, develops female secondary sexual characteristics (breast development, wider hips), and prepares the uterus for pregnancy. Testosterone — Primary male sex hormone produced by testes; responsible for male characteristics (beard, deep voice, muscle mass). Cortisol — Stress hormone produced by adrenal cortex; regulates stress, metabolism, and immunity. Not a sex hormone. Adrenaline — Produced by adrenal medulla; triggers 'fight or flight' response. 📝 Important Note: Female hormones = Oestrogen + Progesterone (by ovaries). Male hormone = Testosterone (by testes). Oestrogen deficiency causes menopause.