Which athlete is most likely to suffer a heat-related illness?

The correct answer is C because an overweight athlete using a wheelchair who is taking laxatives is at a significantly increased risk for heat-related illnesses. This condition can be attributed to a number of factors. Firstly, being overweight often means that the body has a higher volume of tissue that generates heat, making it more difficult for the individual to dissipate heat through normal mechanisms. Secondly, the use of laxatives can result in dehydration, which exacerbates the risk of heat-related illnesses as the body is unable to regulate temperature effectively when dehydrated. Additionally, wheelchair users may have limited ability to dissipate heat due to reduced mobility and may not be able to cool themselves as efficiently as able-bodied athletes.

In contrast, the other options present scenarios that do not carry the same level of risk. An underweight athlete in a cool environment is less likely to overheat, while young athletes in regular athletic gear are typically equipped to manage heat, provided they are not overexerting themselves. A trained athlete wearing light clothing in high temperatures has an advantage due to their conditioning and the breathable nature of their clothing, making them less susceptible to heat-related illnesses compared to an overweight individual with the aforementioned complications.