**Core Concept**
The CuT 380A IUCD is a type of non-hormonal intrauterine contraceptive device (IUCD) that contains 380 milligrams of copper. Its mechanism of action involves the release of copper ions, which exert a spermicidal effect by damaging sperm cells and preventing fertilization.

**Why the Correct Answer is Right**
The CuT 380A IUCD should be replaced every 10 years due to the gradual depletion of copper ions over time. This is because the copper ions are released from the device's surface through a process called diffusion, which leads to a decrease in their concentration over time. As a result, the device's efficacy in preventing pregnancy also decreases. The recommended replacement interval of 10 years is based on clinical trials that have demonstrated the continued effectiveness of the CuT 380A IUCD during this time period.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the CuT 380A IUCD does not need to be replaced annually. The device's copper ions are released gradually over time, and it is not necessary to replace it every year to maintain its efficacy.
**Option B:** This option is incorrect because the CuT 380A IUCD is not designed to be replaced every 5 years. While some IUCDs may require replacement at shorter intervals, the CuT 380A IUCD has been shown to remain effective for 10 years or more.
**Option C:** This option is incorrect because the CuT 380A IUCD does not need to be replaced every 7 years. This option may be a distractor, but it is not based on any scientific evidence or clinical guidelines.

**Clinical Pearl / High-Yield Fact**
The CuT 380A IUCD is one of the most effective forms of reversible contraception available, with a failure rate of less than 1% over 10 years. Its long-term effectiveness makes it a popular choice for women who want a reliable and convenient form of birth control.

**Correct Answer:** C. 7 years