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: B

Rationale: The correct answer is 'physiologist.' A physiologist studies how the body functions under normal and abnormal conditions, including how temperature changes can affect physiological processes like heart rate. An anatomist focuses on the structure of organisms rather than their functions, making choice A incorrect. Choices C and D are also incorrect as they are more related to the study of chemicals and biochemistry, which are not directly relevant to investigating the effects of temperature on heart rate.

Correct Answer: B

Rationale: Homeostasis is the body's ability to maintain stable internal conditions despite external changes. To achieve this balance, concentrations of essential substances must remain within specific ranges. Choice A is incorrect because decreasing concentrations would not maintain stability. Choice C is incorrect as increasing concentrations when the body is stressed would disrupt homeostasis. Choice D is incorrect as fluctuating greatly between high and low values would also not support the body's stability. Therefore, the correct answer is B, as it aligns with the concept of homeostasis by emphasizing the need for stability within certain limits.

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: C

Rationale: The correct answer is C: Absorption of nutrients. The main function of the digestive system is to break down food into nutrients that can be absorbed by the body. Choice A, 'Formation of cells,' is incorrect as cell formation is not the primary function of the digestive system. Choice B, 'Movement of body parts,' is incorrect as this is more related to the muscular system. Choice D, 'Providing oxygen for the extraction of energy from nutrients,' is incorrect because providing oxygen is primarily the function of the respiratory system, not the digestive system.