The factor influencing flexibility that is dependent on individual behaviors is muscle and fat, as it relates to personal activity levels and stretching practices. Unlike joint structure, age, and gender, which are more fixed, muscle and fat can be modified through behavior. Regular stretching and physical activity can enhance flexibility. ;
The factor influencing flexibility that is dependent upon individual behaviors is muscle and fat, as it can be modified through activities like stretching and exercise. Unlike joint structure, age, and gender, which are fixed, muscle and fat can be improved with personal effort. Therefore, the correct answer is B. muscle and fat.
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