What reason contributes to children's decreased ability to handle high temperatures?

The correct answer highlights a significant physiological aspect of children's responses to heat. Children have a lower capacity for skin blood flow compared to adults, which is a critical factor when it comes to thermoregulation in high temperatures.

When exposed to heat, the body typically responds by increasing blood flow to the skin to help dissipate heat through the process of radiation and convection. In children, this response is less efficient due to their reduced skin blood flow. As a result, they may struggle more than adults to dissipate heat effectively, increasing their risk of heat-related illnesses.

In contrast, factors like smaller body size can influence heat retention, but they do not address the fundamental issue of heat dissipation related to blood flow. Similarly, more efficient sweating mechanisms are not characteristic of children; their sweating response is often less mature, which complicates this aspect of thermoregulation. Lastly, while children do have a higher metabolic rate, this can actually lead to greater heat production, which further emphasizes the need for efficient thermoregulation that they often lack. Therefore, recognizing the role of skin blood flow in heat management provides insight into why children may have a decreased ability to handle high temperatures.