The correct answer is D. Increase the resistance to his muscles
Explanation:
The purpose of resistance training is to improve or increase muscular strength. For doing this, the most common method is to increase gradually the weight or intensity of exercise.
This means, in the case of Carl if he finds his muscles have adapted to a specific weight the next step is to increase the resistance by increasing the weight or intensity of the workout because in this way his muscles will begin to adapt to the new intensity or weight and thus his resistance will increase. Therefore, Carl should increase the resistance to his muscles.
