Correct Answer: D

Rationale: The correct answer is 'negative feedback mechanisms.' In biological systems, negative feedback mechanisms help maintain homeostasis by counteracting any deviations from the set point. They work to stabilize internal conditions and keep them within a narrow range. On the other hand, positive feedback mechanisms amplify changes and are not involved in maintaining stability. Choice B, 'an unstable outside environment,' is incorrect as internal stability is independent of external conditions like weather. Choice C, 'decreased atmospheric pressure,' is also incorrect as it does not directly relate to internal homeostasis.

Correct Answer: A

Rationale: The correct answer is A: Body temperature, blood pressure, and pulse rate. Vital signs are measurements that indicate the body's basic functions and are essential indicators of health. Body temperature, blood pressure, and pulse rate are classic vital signs routinely checked in medical settings to assess a person's overall health status. Choices B, C, and D are not considered vital signs. The appearance of the skin, red blood cell count, and oxygen level may provide valuable health information but are not classified as vital signs. Similarly, body weight, age, and gender are important factors in healthcare but are not vital signs. Visual acuity and auditory sharpness relate to sensory functions and are not typically categorized as vital signs.

Correct Answer: A

Rationale: The correct answer is A: Monomers. Macromolecules are built from smaller subunits called monomers. Monomers join together through chemical reactions to form larger molecules known as macromolecules. Option B is incorrect because it does not provide the accurate information regarding macromolecules. Option C is incorrect as it indicates uncertainty, which is not the case here. Option D is incorrect as there is a specific answer related to the composition of macromolecules.

Correct Answer: A

Rationale: The statement provided in the question is true. Ceroid pigments and lipofuscin are products of cellular damage and aging. These substances accumulate within cells over time and can impair cellular functions, including the ability to withstand the damaging effects of oxygen free radicals. Choice B, 'False,' is incorrect because the accumulation of ceroid pigments and lipofuscin does indeed impair a cell's ability to deal with oxidative stress. Choices C and D are also incorrect as the statement is true.

Correct Answer: B

Rationale: In the anatomical position, the palms are facing forward, not backward. Choice A is correct because the head is indeed facing to the front. Choice C is correct as the body is erect. Choice D is correct as the upper limbs are positioned at the sides. Therefore, the incorrect statement is that the palms are facing forward.