1. Antifertility drugs are used in birth control to prevent pregnancy, often steroids like norethindrone.
2. Novestrol (norgestrel) is a synthetic progestin used in contraceptives, correct.
3. Bithionol is an antiseptic; sucralose is a sweetener; terpineol is a fragrance compound, none are antifertility drugs.
4. Thus, the answer is (3) Novestrol.