**Core Concept**
During exercise, the body redistributes blood flow to prioritize active muscles over other areas. This redistribution is crucial for optimizing oxygen delivery and nutrient supply to the exercising muscles. The splanchnic circulation, which supplies blood to the digestive organs, is one of the areas that experience a decrease in blood flow during exercise.

**Why the Correct Answer is Right**
The decrease in splanchnic blood flow during exercise is mainly due to the sympathetic nervous system's activation of alpha-adrenergic receptors on the smooth muscle cells of splanchnic arteries. This activation leads to vasoconstriction, which reduces blood flow to the digestive organs. This response is part of the body's overall effort to redirect blood flow to the exercising muscles and maintain blood pressure.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the decrease in splanchnic blood flow during exercise.
* **Option B:** Vasodilation is the opposite of what occurs in the splanchnic circulation during exercise.
* **Option D:** This option does not accurately describe the mechanism responsible for the decrease in splanchnic blood flow.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the splanchnic circulation is not the only area affected by the redistribution of blood flow during exercise. Other areas, such as the skin and kidneys, also experience decreased blood flow to prioritize the exercising muscles.

**Correct Answer:** C. Activation of alpha-adrenergic receptors on splanchnic arteries leading to vasoconstriction.