**Core Concept**
Emergency contraception is recommended to prevent pregnancy after unprotected sexual intercourse. The most effective method is levonorgestrel, which works by inhibiting or delaying ovulation.

**Why the Correct Answer is Right**
Levonorgestrel, a progestin-only emergency contraceptive, is effective when taken within 72 hours of unprotected sex. It acts by inhibiting the luteinizing hormone surge, thereby preventing ovulation. This mechanism is mediated through the hypothalamic-pituitary-adrenal axis, specifically by the GnRH receptor. The effectiveness of levonorgestrel decreases with time, making it essential to administer the medication as soon as possible.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not a recognized emergency contraceptive method. Intrauterine devices (IUDs) are effective for long-term contraception but not specifically indicated for emergency contraception.
**Option B:** Copper IUDs are effective for emergency contraception when inserted within 5 days of unprotected sex, but this option does not specify the method.
**Option C:** This option is incorrect as it does not provide a specific method for emergency contraception.

**Clinical Pearl / High-Yield Fact**
Emergency contraception should be offered to all women who have had unprotected sex, regardless of their menstrual cycle or fertility status.

**Correct Answer: B. Copper IUDs are effective for emergency contraception when inserted within 5 days of unprotected sex.**