**Core Concept**
The question is testing the knowledge of Intrauterine Devices (IUDs) and their failure rates. IUDs are a type of long-acting reversible contraceptive method that prevents pregnancy by various mechanisms, including the release of hormones or copper ions.

**Why the Correct Answer is Right**
The failure rate of an IUD is determined by its ability to prevent implantation of a fertilized egg or interfere with ovulation. Among the available options, the **Copper T 380A** IUD has a low failure rate due to its high surface area, which allows for the release of copper ions that create an environment inhospitable to sperm and fertilization. This results in a failure rate of less than 1% over five years. The copper ions also increase the viscosity of cervical mucus, making it more difficult for sperm to reach the egg.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not specify a particular type of IUD. Without more information, it is difficult to determine the failure rate.
* **Option B:** This option may refer to a hormonal IUD, such as the Mirena or Skyla. However, hormonal IUDs have a higher failure rate compared to copper IUDs, especially in the first year of use.
* **Option D:** This option is incorrect because it does not correspond to a known type of IUD.

**Clinical Pearl / High-Yield Fact**
When counseling patients about IUDs, it is essential to inform them that copper IUDs can cause heavier menstrual bleeding and cramping, while hormonal IUDs can lead to irregular bleeding and amenorrhea.

**Correct Answer: C. Copper T 380A**