## **Core Concept**
The right coronary artery (RCA) is one of the two main coronary arteries that arise from the aorta, supplying blood to the heart. It typically arises from the anterior aortic sinus and supplies a significant portion of the right atrium and right ventricle. The RCA's distribution and dominance can vary among individuals.

## **Why the Correct Answer is Right**
The statement that **b) RCA arises from anterior aortic sinus** is true. The RCA typically originates from the anterior aortic sinus, one of the three sinuses of the aortic root. This anatomical detail is crucial for understanding coronary artery anatomy and for procedures like coronary angiography.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Diameter less than LCA - While it's generally true that the RCA and left coronary artery (LCA) can vary in size, and the LCA often has a larger diameter because it supplies more myocardium, this statement isn't universally true and doesn't directly relate to a specific, defining characteristic of the RCA like its origin.
- **Option C:** RCA supplies major part of right atrium and right ventricle - This is largely true but let's evaluate all options. The RCA does supply a significant portion of the right atrium and right ventricle, but the extent can vary. However, the specificity and universality of this statement compared to the origin might make it less distinctly correct.
- **Option D:** RCA gives rise to circumflex coronary branch - This is generally incorrect in a typical coronary circulation. The circumflex coronary artery usually arises from the left coronary artery (LCA), not the RCA. The RCA may give off branches like the right marginal artery and the posterior descending artery (PDA) in a right-dominant system but not typically the circumflex.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that the RCA usually supplies the **SA node** (sinoatrial node) and often the **AV node** (atrioventricular node), and in about 85-90% of individuals, it exhibits a **right dominance**, meaning it gives off the posterior descending artery (PDA).

## **Correct Answer: B. RCA arises from anterior aortic sinus**