**Core Concept**
Blood distribution among different vascular beds is a critical aspect of hemodynamics. The majority of the blood is present in the capillaries, where gas exchange and nutrient uptake occur.

**Why the Correct Answer is Right**
The correct answer is 5%. This is because capillaries have the largest total cross-sectional area of all blood vessels, approximately 6,300 cm^2/m^2 body surface area. This large surface area allows for optimal exchange of oxygen, carbon dioxide, nutrients, and waste products between the blood and tissues.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it overestimates the proportion of blood in capillaries. While the total volume of capillary blood is significant, it represents only a small fraction of the total blood volume.
* **Option B:** This option is incorrect because it implies that the majority of blood is present in arterioles, which is not the case. Arterioles are primarily involved in regulating blood pressure and flow.
* **Option C:** This option is incorrect because it suggests that the majority of blood is present in venules, which is also not accurate. Venules are primarily involved in collecting deoxygenated blood from the capillaries.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the capillary bed is the site of gas exchange and nutrient uptake, and its large surface area allows for optimal exchange between the blood and tissues.

**Correct Answer:** C. 5%