Which of the following symptoms indicates mild or moderate hypothermia?

Mild to moderate hypothermia is characterized by the body's core temperature dropping, which leads to a variety of physiological responses. Shivering is one of the hallmark symptoms of mild hypothermia, as it is the body's natural mechanism to generate heat. Stumbling or a lack of coordination can indicate that the body is beginning to struggle to function properly due to the cold, affecting motor skills and cognitive abilities.

In contrast, the other symptoms listed do not align with mild to moderate hypothermia. Excessive sweating most commonly occurs in the presence of heat, not in cold-related conditions, indicating a more active metabolic state contrary to hypothermia. Bright red skin and a rapid heartbeat can denote other medical issues, such as heat-related illnesses, not hypothermia. Lastly, extreme thirst and dizziness could signify dehydration or heat exhaustion rather than symptoms associated with the onset of hypothermia. Therefore, shivering and stumbling effectively reflect the body's struggle against hypothermia, making this the correct choice.