**Core Concept**
The Alvarado score is a clinical scoring system used to diagnose acute appendicitis, incorporating various symptoms, signs, and laboratory findings. It helps clinicians assess the likelihood of appendicitis in patients presenting with abdominal pain. The score ranges from 0 to 10, with higher scores indicating a higher probability of appendicitis.

**Why the Correct Answer is Right**
The Alvarado score assigns points for symptoms such as migration of pain, anorexia, nausea/vomiting, and tenderness in the right iliac fossa, as well as for laboratory findings like elevated temperature and leukocytosis. A score of 2 is assigned for the symptom of rebound abdominal tenderness, which is a significant indicator of peritoneal irritation, a common feature of acute appendicitis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not correspond to the symptom or sign that is assigned a score of 2 in the Alvarado score.
**Option B:** Similarly, this option does not match the criteria for a score of 2.
**Option D:** This option also does not align with the Alvarado score's criteria for a score of 2.

**Clinical Pearl / High-Yield Fact**
The Alvarado score is a useful tool in the emergency department for quickly assessing patients with suspected appendicitis, helping to decide who may require urgent surgical intervention. Remembering the components and their respective scores is crucial for efficient patient evaluation.

**Correct Answer:** Correct Answer: C. Rebound tenderness (also known as Blumberg's sign).