## **Core Concept**
The abortion stick, a traditional method used for inducing abortion, primarily works through mechanical and pharmacological means. The sticks used are often impregnated with certain substances that stimulate uterine contractions. Understanding its mechanism involves knowledge of uterine stimulation and the substances that can induce labor or abortion.

## **Why the Correct Answer is Right**
The correct answer, **C. Prostaglandins**, is right because the abortion stick is believed to contain substances that release prostaglandins. **Prostaglandins** are known to stimulate uterine contractions. They play a crucial role in the initiation of labor and can induce abortion when used appropriately. The use of prostaglandins, specifically **PGE2 (Dinoprostone)**, is a well-established medical method for inducing labor and abortion, supporting the mechanism of action of substances that might be present on abortion sticks.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because while certain substances might affect the uterus, **progesterone** actually supports pregnancy by maintaining the endometrium. It does not induce abortion.
- **Option B:** This option is incorrect as there is no commonly recognized direct pathway for inducing abortion related to **oxytocin receptors** being the primary mechanism of action for substances on abortion sticks, although oxytocin does stimulate uterine contractions.
- **Option D:** This option is incorrect because **estrogen** does not directly induce uterine contractions leading to abortion. Estrogen levels do rise during pregnancy but inducing abortion is not a direct effect.

## **Clinical Pearl / High-Yield Fact**
A memorable point for exams is that **prostaglandins (like PGE2) are used clinically** to induce labor and can cause abortion if used inappropriately or at certain stages of pregnancy. This highlights the importance of understanding both the medical use and potential misuse of such substances.

## **Correct Answer:** C. Prostaglandins