## **Core Concept**
The definitive signs of pregnancy are those that confirm the presence of a fetus and are typically identified through medical examination or imaging. These signs are crucial for diagnosing pregnancy with certainty.

## **Why the Correct Answer is Right**
The correct answer, **C. Fetal parts felt on palpation**, is a definitive sign of pregnancy because it directly confirms the presence of a fetus. This is usually done during a physical examination where a healthcare provider can feel the different parts of the fetus (like the head, back, and limbs) through the abdominal wall. This requires a certain level of fetal development and positioning that makes it possible, typically after the first trimester.

## **Why Each Wrong Option is Incorrect**
- **Option A: Amenorrhea** is a presumptive sign of pregnancy. It simply indicates that a woman has missed her periods, which can be due to pregnancy but also many other reasons such as stress, hormonal imbalances, or other medical conditions.
- **Option B: Breast tenderness** is also a presumptive sign. It can occur due to pregnancy but is also a common symptom of the premenstrual syndrome and other hormonal changes.
- **Option D: Quickening** (the sensation of the fetus moving) is considered a presumptive sign as well. While it suggests the presence of a fetus, it can be misinterpreted as gas movements or other abdominal sensations.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that definitive signs of pregnancy include not just feeling fetal parts on palpation but also hearing the fetal heartbeat (via Doppler or fetoscope) and seeing the fetus on ultrasound. These signs are critical for confirming pregnancy and are often used in clinical practice to establish a definitive diagnosis.

## **Correct Answer:** C. Fetal parts felt on palpation