Factors that can increase a person's likelihood of heat illness include ____.

The correct answer encompasses all factors listed, as each contributes to an increased risk of heat illness in different ways.

Poor physical condition can significantly reduce a person's ability to cope with high temperatures. Individuals who are not physically fit may have compromised cardiovascular efficiency, making their bodies less capable of effectively regulating temperature through sweating and circulation.

Heart problems also play a crucial role in this context. Those with existing heart conditions may have a reduced ability to manage increased bodily stress due to heat, leading to complications more likely than in healthy individuals.

Weight is another important factor. Excess body weight can impede the body's natural cooling processes and increase the metabolic heat generated during physical exertion. Overweight individuals may experience a heightened risk for overheating during periods of high temperatures or strenuous activity.

All these factors—poor physical condition, heart issues, and excess weight—interact to elevate the risk of heat illness, making the comprehensive answer that includes all of them the most accurate.