**Core Concept**
Mean arterial pressure (MAP) is the average blood pressure in the arteries during one cardiac cycle. It is a critical parameter in assessing cardiovascular function and perfusion of vital organs. MAP is influenced by cardiac output, systemic vascular resistance, and the compliance of the arterial system.

**Why the Correct Answer is Right**
The correct answer is **A. Cardiac output**, as it is the primary determinant of MAP. Cardiac output is the product of heart rate and stroke volume, and it directly affects the pressure generated by blood flow in the arteries. According to the Guyton's theory, cardiac output is the main determinant of MAP, accounting for approximately 80% of its variability. The remaining 20% is influenced by systemic vascular resistance and the compliance of the arterial system.

**Why Each Wrong Option is Incorrect**
**Option B:** While systemic vascular resistance (SVR) does contribute to MAP, it is not the primary determinant. SVR is influenced by factors like blood vessel diameter, smooth muscle tone, and blood viscosity.
**Option C:** Arterial compliance, or the ability of arteries to distend and accommodate blood volume, is an important factor in blood pressure regulation. However, it is not the primary determinant of MAP.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that mean arterial pressure is a critical parameter in assessing cardiovascular function, particularly in patients with shock or cardiac failure. A decrease in MAP can lead to inadequate perfusion of vital organs, resulting in tissue hypoxia and multi-organ dysfunction.

**Correct Answer:** A. Cardiac output