Correct Answer: B

Rationale: A variety of foods is the best source of nutrients because it ensures a balanced intake of all essential nutrients required by the body. Option A, specific food combinations, may not provide all necessary nutrients as relying on only a few types of food may lead to deficiencies. Option C, individual foods, also may not provide a complete range of nutrients necessary for overall health. Option D, a variety of food supplements, is not the best source of nutrients as whole foods are generally more beneficial due to their natural nutrient composition and bioavailability.

Correct Answer: B

Rationale: 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.

Correct Answer: C

Rationale: The correct answer is C: 'muscular and chemical.' In the process of digestion, muscular movements help in mixing and propelling food along the digestive tract, while chemical breakdowns involving enzymes and acids break down food into smaller molecules for absorption. Choices A, B, and D are incorrect as thermal, segmental, and mechanical actions are not the primary actions involved in the digestion process.

Correct Answer: A

Rationale: The correct answer is A: provide energy. Nutrients play a crucial role in providing energy for the body's various functions. While they do help in regulating metabolic processes and in building and repairing tissue, the primary function related to energy production. Choices B, C, and D are incorrect as nutrients are not primarily responsible for controlling cellular wastes, hormone levels, or absorption.

Correct Answer: C

Rationale: The recommended fat intake is between 20% to 35% of total daily calories. This range is considered optimal for maintaining a healthy diet. Choice A (10% to 15%) is too low and might not provide enough essential fats for the body. Choice B (10% to 35%) includes an upper limit that exceeds the generally accepted range. Choice D (40% to 55%) suggests a fat intake that is higher than what is recommended, which could lead to health issues if consumed regularly.