Regarding starvation:

Correct Answer: B

Rationale: Step-by-step rationale for the correct answer (B): 1. During starvation, the body shifts to using ketoacids derived from fats for fuel. 2. The brain and other tissues can utilize these ketoacids. 3. This process helps to spare protein and prevent muscle breakdown. 4. Therefore, choice B is correct as ketoacids play a crucial role in providing energy during starvation. Summary of why other choices are incorrect: A: Glycogen stores are depleted within 24 hours, not 48 hours. C: Hypoglycemia during starvation does not have a protein sparing effect. D: The average time until death from starvation is typically much shorter than 40 days.

Correct Answer: C

Rationale: The correct term for the digestive tract that begins at the mouth and finishes at the anus is called the alimentary canal. This term specifically refers to the entire passage through which food passes and is digested. The term "alimentary" pertains to nourishment or nutrition, making it the most accurate description of the digestive tract. A: Digestive passage is too broad and vague, not specifying the entire route of digestion. B: Elementary canal is not a commonly used term in anatomy to describe the digestive tract. D: Intestinal tract specifically refers to the section of the digestive system that includes the small and large intestines, excluding the mouth, esophagus, and stomach.

Correct Answer: D

Rationale: The correct order is D: Duodenum, jejunum, ileum. The duodenum is the first part of the small intestine connected to the stomach for digestion. Next is the jejunum, where most of the nutrients are absorbed. Lastly, the ileum completes the absorption process before reaching the large intestine. Choice A is incorrect as it has the parts in the wrong order. Choice B also has the parts in the wrong order. Choice C has the duodenum and ileum in the correct position but switches the jejunum and ileum.

Correct Answer: A

Rationale: The correct answer is A because it states that none of the above choices are similarities between hormones and neurotransmitters. This is accurate as choices B, C, and D all highlight similarities between hormones and neurotransmitters. Choice B is correct as both are chemical messengers, choice C is correct because some hormones and neurotransmitters can be chemically identical, and choice D is correct because both produce molecules that act on receptors. Therefore, A is the correct choice as it states that there are no similarities between the two, which is not the case.

Correct Answer: C

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.