What factor is most likely to influence an individual's fitness level?

The choice that highlights genetics combined with lifestyle choices as the most influential factor on an individual's fitness level is accurate because both elements interact significantly to shape physical capabilities and overall health. Genetics can define the potential for certain athletic traits, such as muscle composition, endurance, and recovery speed, while lifestyle choices encompass a range of behaviors including diet, exercise habits, and overall activity levels.

This means an individual could have a genetic predisposition for athletic performance but may not reach their potential without a suitable lifestyle that includes regular exercise and proper nutrition. Conversely, someone with less favorable genetics may still achieve a high fitness level through disciplined lifestyle choices and training. Therefore, the best understanding of fitness levels recognizes the interdependence of these factors rather than attributing fitness to just one aspect, such as age, dietary preferences, or specific types of exercise alone.