**Core Concept**
The question pertains to the mechanism of action of an abortion stick, an instrument sometimes used in criminal abortions. This involves understanding the **physiological and anatomical principles** of pregnancy termination.

**Why the Correct Answer is Right**
The correct mechanism involves introducing a foreign object into the uterus, which leads to **infection and initiation of uterine contractions**. This can cause the uterus to expel its contents, thereby terminating the pregnancy.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect as it doesn't relate to the direct action of an abortion stick.
**Option B:** Also incorrect, lacking relevance to the specific mechanism of action of an abortion stick.
**Option C:** Not applicable, as it doesn't describe the mechanism by which an abortion stick works.
**Option D:** Incorrect, not describing the action of an abortion stick.

**Clinical Pearl / High-Yield Fact**
It's crucial to remember that such methods are unsafe and can lead to severe **infections and long-term reproductive damage**.

**Correct Answer:** D. Introduction of infection and initiation of uterine contractions.