Correct Answer: C

Rationale: The correct answer is C because essential fatty acids are not manufactured by the body and must be obtained through the diet. Choice A is incorrect because essential fatty acids can come from plant sources as well. Choice B is incorrect as essential fatty acids are primarily derived from plant sources. Choice D is incorrect because essential fatty acids cannot be produced by the body. Therefore, the only accurate statement is that essential fatty acids are not manufactured by the body.

Correct Answer: D

Rationale: The Dietary Reference Intake (DRI) for protein is primarily determined by an individual's body weight. This is because the body's protein requirement is proportionate to its size, which is generally reflected in the body weight. Therefore, choice D is correct. Choices A, B, and C are incorrect: While factors such as fatty acid intake, gender, and height can influence an individual's overall nutritional needs, they do not directly determine the DRI for protein.

Correct Answer: A

Rationale: The correct answer is A: vitamin B12. Intrinsic factor is a glycoprotein produced by the stomach that is necessary for the absorption of vitamin B12 in the small intestine. Vitamin B12 binds to intrinsic factor in the stomach, forming a complex that is then absorbed in the ileum. This absorption process is crucial for preventing vitamin B12 deficiency. Choices B, C, and D are incorrect because they do not require intrinsic factor for absorption. Folate is absorbed in the small intestine through a different mechanism, niacin can be absorbed in the small intestine without the need for intrinsic factor, and vitamin B6 does not rely on intrinsic factor for absorption.

Correct Answer: A

Rationale: Salmon is the correct answer as it is a rich source of omega-3 fatty acids, specifically EPA and DHA, which are known to be beneficial for heart health. Chicken, spinach, and eggs do not contain significant levels of omega-3 fatty acids compared to salmon. While eggs do contain some omega-3s, the amount is considerably lower than what is found in fatty fish like salmon.

Correct Answer: A

Rationale: Carbohydrates are composed of carbon, hydrogen, and oxygen. These three elements combine to form the basic structure of carbohydrates. Oxygen is an essential element in carbohydrates, contributing to their chemical composition. Choice B (nitrogen) is incorrect as nitrogen is not a typical component of carbohydrates. Choice C (water) is incorrect as water is not an element but a compound composed of hydrogen and oxygen. Choice D (glucose) is incorrect as glucose is a specific type of sugar, not an element found in the composition of carbohydrates.