**Core Concept**
The expulsion rate of an Intrauterine Device (IUD) is an important consideration in the management of contraception. It refers to the percentage of women who experience the device being expelled from the uterus, often within the first few weeks or months after insertion.

**Why the Correct Answer is Right**
The expulsion rate of an IUD is influenced by several factors, including the type of IUD, the size and shape of the uterus, and the skill of the healthcare provider inserting the device. The lowest expulsion rate is typically seen with the ParaGard (copper IUD), which has a smaller size and a more flexible frame compared to other IUDs.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the Mirena (levonorgestrel-releasing IUD) has a higher expulsion rate compared to the ParaGard, primarily due to its larger size and more rigid frame.
**Option B:** This option is incorrect because the Skyla (levonorgestrel-releasing IUD) has a similar expulsion rate to the Mirena, and is not known for having the lowest expulsion rate among IUDs.
**Option C:** This option is incorrect because the Liletta (levonorgestrel-releasing IUD) has a higher expulsion rate compared to the ParaGard, primarily due to its larger size and more rigid frame.

**Clinical Pearl / High-Yield Fact**
It's essential for healthcare providers to carefully assess the uterine cavity and select the appropriate IUD size and type to minimize the risk of expulsion and ensure effective contraception.

**Correct Answer: A. ParaGard**