Which of the following is a sign of the onset of hypothermia?

The onset of hypothermia is indicated by specific physiological responses of the body to excessive cold exposure. As the body's core temperature begins to drop, shivering becomes a crucial response aimed at generating heat. In the case mentioned, as cold stress intensifies, the shivering can become more pronounced, and individuals may experience a noticeable impairment in their ability to perform complex tasks. This occurs because the brain's functioning is affected by the decreasing body temperature, leading to confusion and difficulty with coordination.

The other choices present symptoms that can be associated with more severe stages of hypothermia or other conditions but do not accurately represent the initial signs. For example, intense muscle rigidity, loss of consciousness, or severe joint issues tend to arise in later stages, while mild shivering and loss of memory could be more varied or attributed to other factors. Thus, the selected answer aptly captures the critical signs during the early phase of hypothermia, offering insight into how the body responds significantly to cold exposure.