## Core Concept
The triangle of auscultation is a relative thinning of the musculature of the back, making it an optimal location for auscultating lung sounds. It is defined by specific anatomical landmarks.

## Why the Correct Answer is Right
The triangle of auscultation is bounded by the latissimus dorsi muscle (inferolaterally), the trapezius muscle (superolaterally), and the medial border of the scapula (medially). The rhomboid muscles lie beneath or are closely related to these boundaries but are not considered a boundary of the triangle itself.

## Why Each Wrong Option is Incorrect
- **Option A:** The latissimus dorsi muscle forms one of the boundaries, specifically the inferior and lateral border.
- **Option B:** The trapezius muscle forms another boundary, specifically the superior and lateral border.
- **Option D:** The medial border of the scapula forms the medial boundary.

## Why Option C is Incorrect
- **Option C:** The rhomboid muscles, while in the vicinity and related to the scapula, do not form a boundary of the triangle of auscultation. They lie deeper and are not considered part of the superficial boundaries.

## Clinical Pearl / High-Yield Fact
The triangle of auscultation becomes more prominent when the patient is asked to cross their arms and lean forward, which helps to move the scapulae and muscles away from the spine, making lung auscultation easier.

## Correct Answer: C. Rhomboid muscle.