**Core Concept**
Emergency contraception is a method of preventing pregnancy after unprotected intercourse. It works by delaying or inhibiting ovulation, altering the uterine environment, or interfering with fertilization. Various options are available, including hormonal and non-hormonal methods.

**Why the Correct Answer is Right**
LNG IUD, or Levonorgestrel-releasing Intrauterine Device, is a highly effective form of long-term contraception and not typically used as an emergency contraceptive. LNG IUD releases a continuous dose of levonorgestrel, a progestin, which prevents ovulation and fertilization over a prolonged period. While it can be used as a regular contraceptive method, it is not the best choice for emergency contraception due to its delayed onset of action and the need for insertion by a healthcare provider.

**Why Each Wrong Option is Incorrect**
**Option B:** Oral Mifepristone, also known as RU-486, is a progesterone receptor antagonist that can be used as an emergency contraceptive to prevent implantation of a fertilized egg. It is effective when taken within 72 hours of unprotected intercourse.
**Option C:** Oral Levonorgestrel, also known as Plan B or the morning-after pill, is a progestin-only emergency contraceptive that can prevent ovulation or fertilization when taken within 72 hours of unprotected intercourse.
**Option D:** Cu-containing IUD, or Copper-releasing Intrauterine Device, is a non-hormonal emergency contraceptive that can be inserted up to 5 days after unprotected intercourse to prevent fertilization. It works by releasing copper ions, which are toxic to sperm.

**Clinical Pearl / High-Yield Fact**
It is essential to note that emergency contraceptives are most effective when taken as soon as possible after unprotected intercourse. The timing and effectiveness of each method can vary, and patients should be counseled accordingly.

**✓ Correct Answer: A. LNG IUD**