A person who engages in aerobic exercise but does not focus on building muscle could experience different outcomes, but the most likely prediction based on the options provided is:
A. Person's metabolism would be slow from lack of muscle.
Muscle tissue is metabolically active, meaning it burns more calories at rest compared to fat tissue. Therefore, if a person does not engage in strength training to build or maintain muscle mass, their overall metabolic rate may be lower than if they also included muscle-building activities in their routine.
While some weight loss may occur due to the calorie-burning effects of aerobic exercise, without muscle-building efforts, there may also be potential for a person to lose muscle mass over time, which could further decrease their metabolism. Options B and C could happen depending on various factors such as overall diet, duration of exercise, and individual metabolism, but option A best reflects a primary physiological consequence of not building muscle alongside aerobic exercise.