Vasodilation Causes Skin Redness

Steps:

• Heat triggers the body's thermoregulation to cool down.
• Blood vessels in the skin respond by widening.
• This increases blood flow near the surface.
• More visible blood makes skin appear red.

Why A is correct:

• Vasodilation of arteries increases blood volume in skin capillaries, enhancing redness via visible hemoglobin, per circulatory physiology.

Why the others are wrong:

• B: Capillaries don't move; dilation allows more blood flow without relocation.
• C: Sweating cools the body but doesn't cause redness; it's evaporative cooling.
• D: Temperature receptors remain active to detect and respond to heat.

Final answer: A