Correct Answer: C

Rationale: The correct answer is 'impaired cell division and the ability to break down and recycle worn cell parts.' Aging at the cellular level involves reduced efficiency in cell division and the breakdown/recycling of cellular components, leading to functional decline. Choices A, B, and D are incorrect because they involve external physical manifestations or organ-specific issues rather than cellular-level changes associated with aging.

Correct Answer: C

Rationale: Simple squamous epithelium is a type of tissue, not an organ system, organ, or molecule. Tissues are groups of cells that work together to perform a specific function. In this case, simple squamous epithelium is a thin, single layer of flattened cells that line surfaces involved in passive diffusion, such as the alveoli in the lungs or blood vessels. Therefore, the correct answer is 'tissue.' Choices A, B, and D are incorrect as they do not accurately categorize simple squamous epithelium as a tissue.

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: D

Rationale: The correct answer is 'sagittal.' A sagittal section divides the body into right and left portions. Choice A, 'frontal,' is incorrect as it divides the body into front and back portions. Choice B, 'transverse,' divides the body into upper and lower portions. Choice C, 'coronal,' divides the body into anterior and posterior portions. Therefore, 'sagittal' is the most appropriate term for a section separating the body into right and left portions.

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.