Final answer:
The correct answer is Option D. Temperature regulation by the skin is achieved through vasodilation and vasoconstriction which help maintain body temperature homeostasis.
Step-by-step explanation:
Temperature regulation by the skin is accomplished through vasodilation and vasoconstriction. These processes are part of the thermoregulation abilities of the integumentary system. When the body temperature rises, the hypothalamus signals the sweat glands to release sweat and causes blood vessels in the dermis to dilate. This increases blood flow near the body's surface to dissipate heat into the environment through radiation and evaporation. Conversely, when the body temperature decreases, the blood vessels constrict, bringing blood to the core to conserve heat around vital organs. These mechanisms help maintain homeostasis of body temperature essential for optimal physiological functioning.