Final answer:
Sex, age, and the size of the person are all factors that determine the maximal oxygen uptake.
Step-by-step explanation:
The factors that help determine the maximal oxygen uptake (VO2 max) include sex, age, and the size of the person. Male individuals typically have a higher VO2 max compared to females, partly due to differences in body composition and hemoglobin levels. As a person ages, their VO2 max generally decreases, which is often a result of reduced physical activity levels and physiological changes. The size of a person also affects VO2 max; larger individuals may have a higher absolute VO2 max due to greater muscle mass, but when adjusting for body weight, this may not be the case. Therefore, all options provided, which are sex, age, and size of the person, play a role in determining maximal oxygen uptake.