Correct Answer: B

Rationale: The correct answer is B: 'be obtained by the diet.' Essential nutrients are those that the body cannot synthesize in sufficient quantities and must therefore be obtained through the diet. Choice A is incorrect because not all essential nutrients need to be consumed daily; the frequency of consumption varies. Choice C is incorrect because not all essential nutrients are water-soluble; they can be water-soluble or fat-soluble. Choice D is incorrect because essential nutrients do not need to be consumed at every meal, but rather need to be included in the overall diet regularly.

Correct Answer: D

Rationale: The correct answer is D: vitamins A, E, K, and D. Fat-soluble vitamins are absorbed along with fats in the diet and can be stored in the body's fatty tissue. Vitamins B and C are water-soluble vitamins and are not stored in the body; any excess amounts are usually excreted in the urine. Therefore, choices A, B, and C are incorrect.

Correct Answer: A

Rationale: The correct answer is A: 'they must be supplied by the diet.' Essential fatty acids, like omega-3 and omega-6, cannot be produced by the body and must be obtained through the diet. They are polyunsaturated fatty acids, playing vital roles in inflammation and cell membrane structure. Choice B is incorrect because essential fatty acids cannot be produced by dehydrogenation, a process of removing hydrogen. Choice C is incorrect as not all essential fatty acids are anti-inflammatory; some have pro-inflammatory roles. Choice D is incorrect because not all essential fatty acids are polyunsaturated; omega-9, for example, is a monounsaturated essential fatty acid.

Correct Answer: C

Rationale: The correct answer is C: Daily physical activity. Daily physical activity contributes to better flexibility, balance, endurance, and overall health, helping older adults maintain independence and reduce the risk of chronic diseases. Choices A, B, and D, although important for overall health, do not specifically address the benefits of greater flexibility, better balance, more endurance, and greater longevity associated with daily physical activity.

Correct Answer: A

Rationale: Both statements are indeed true. Many adolescents undergoing orthodontic treatment often neglect proper nutrition and oral hygiene, leading to subpar practices in these areas. It's common for them to be less attentive to these aspects due to various factors. A dental hygienist's role includes motivating these patients towards better self-care practices. One effective approach is by emphasizing that good nutrition and oral hygiene can significantly enhance their appearance. This approach is particularly effective for adolescents as they are often highly conscious about their looks. The other choices are incorrect because they suggest that one or both of the statements are false, which is not the case.