Final answer:
Both Brad and Trevor have different physical strengths—Brad in strength and Trevor in endurance—which contribute to their physical fitness. However, fitness has many components, and both can work on improving their overall fitness levels. Hence, option d. is correct.
Step-by-step explanation:
The question relates to physical fitness and compares the abilities of two individuals, Brad and Trevor. Based on the information provided, Brad has significant strength but lacks endurance, while Trevor has endurance but less strength. When considering physical fitness, it is important to recognize that it has multiple components, including strength, endurance, flexibility, body composition, and more.
Therefore, to determine who is more physically fit, one must consider all aspects of fitness. Natural selection, mentioned in portion 'a' of the provided reference, indeed favors traits that improve an organism's chances of survival and reproduction, such as better running speed for those who run frequently. However, this does not directly relate to the fitness of Brad or Trevor.
In this context, the most accurate answer would be option d. Both Brad and Trevor can improve their physical fitness.' This acknowledges that both individuals have areas where they excel and areas where they can grow. Physical fitness is not solely about being the strongest or the fastest; it's also about a balanced and comprehensive level of health and well-being.