**Core Concept**
Bernoulli's theorem is a fundamental concept in fluid dynamics that explains the relationship between the pressure and velocity of fluid flow. It states that an increase in the velocity of a fluid results in a decrease in its pressure, and vice versa. This principle is crucial in understanding various physiological and pathological processes in the human body.

**Why the Correct Answer is Right**
The correct application of Bernoulli's theorem can be observed in the physiology of blood flow through the circulatory system. As blood flows through the arteries, its velocity increases, resulting in a decrease in pressure. This is why the pressure in the aorta is higher than in the peripheral arteries. The theorem also explains the phenomenon of turbulence in blood flow, which can lead to the formation of thrombi and emboli. The key concept here is the relationship between velocity and pressure, which is governed by Bernoulli's equation: P + 1/2ρv^2 + ρgy = constant, where P is pressure, ρ is density, v is velocity, g is acceleration due to gravity, and y is height.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Bernoulli's theorem does not explain the relationship between blood pressure and cardiac output.

**Option B:** This option is incorrect because Bernoulli's theorem is not directly related to the concept of viscosity in fluid dynamics.

**Option C:** This option is incorrect because Bernoulli's theorem does not explain the mechanism of blood clotting.

**Clinical Pearl / High-Yield Fact**
A key clinical application of Bernoulli's theorem is in the diagnosis and management of aortic stenosis, where the increased velocity of blood flow through the narrowed aortic valve results in a decrease in pressure, leading to symptoms of chest pain and shortness of breath.

**Correct Answer:** C.