**Core Concept**
During exercise, the body undergoes various physiological changes to meet the increased energy demands. One of these changes involves the regulation of blood flow to the muscles, which is mediated by the autonomic nervous system and the vascular system.

**Why the Correct Answer is Right**
The correct answer is related to the vasodilation of blood vessels during exercise. This occurs due to the release of certain neurotransmitters and hormones, such as acetylcholine and adrenaline, which stimulate the smooth muscle cells of blood vessels to relax, leading to an increase in blood flow to the muscles. This vasodilation is essential to provide the necessary oxygen and nutrients to the exercising muscles.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the physiological change that occurs during exercise.
**Option B:** This option is incorrect because it is not directly related to the regulation of blood flow during exercise.
**Option C:** This option is incorrect because it describes a decrease in blood flow, which is the opposite of what occurs during exercise.

**Clinical Pearl / High-Yield Fact**
During intense exercise, the body's ability to vasodilate blood vessels can be impaired due to heat stress, leading to a decrease in exercise performance. This is known as heat intolerance.

**Correct Answer: C. Decrease in peripheral resistance.**