The body of scientific knowledge related to nutritional requirements for human growth, maintenance, activity, and reproduction is known as:

The correct answer is B: nutrition science. Nutrition science specifically focuses on studying the requirements and functions of nutrients in relation to human growth, maintenance, activity, and reproduction. Choice A, physiology, deals more with the functions of living organisms and their parts, not specifically related to nutrients. Choice C, biochemistry, focuses on the chemical processes and substances that occur within living organisms, not specifically centered on nutritional requirements. Choice D, dietetics, involves the application of nutritional knowledge in planning and managing diets for individuals, but it is more focused on the practical aspect rather than the broader scientific study of nutritional requirements.