**Core Concept**
Pulse pressure is the difference between the systolic and diastolic blood pressures. It is an important indicator of vascular compliance and cardiac output. The factors that affect pulse pressure are related to changes in blood volume, heart rate, and vascular resistance.

**Why the Correct Answer is Right**
Aortic stiffness, cardiac output, and peripheral resistance are the key factors that influence pulse pressure. An increase in cardiac output or a decrease in peripheral resistance leads to an increase in pulse pressure. Conversely, a decrease in cardiac output or an increase in peripheral resistance results in a decrease in pulse pressure. For instance, in conditions like aortic stenosis, the increased resistance to ejection of blood from the heart increases the systolic blood pressure, thereby increasing the pulse pressure.

**Why Each Wrong Option is Incorrect**
* **Option A:** While age can affect vascular compliance and cardiac output, it is not a direct factor that affects pulse pressure.
* **Option B:** Although systemic vascular resistance is related to blood pressure, it is not a direct factor that affects pulse pressure.
* **Option D:** Blood volume can affect cardiac preload and output, but it is not a direct factor that affects pulse pressure.

**Clinical Pearl / High-Yield Fact**
Aortic stiffness, particularly in older adults, can lead to an increase in pulse pressure, which is an independent risk factor for cardiovascular disease.

**Correct Answer:** C. Aortic stiffness, cardiac output, and peripheral resistance.