Correct Answer: A

Rationale: Melatonin is the hormone produced by the pineal gland that plays a crucial role in regulating sleep-wake cycles and is associated with the body's internal circadian rhythm. Melatonin levels typically rise in the evening, signaling to the body that it is time to sleep, and decrease in the morning, helping to wake up and feel alert. Serotonin, dopamine, and endorphins are neurotransmitters that serve different functions in the body and are not primarily responsible for regulating sleep-wake cycles. Serotonin is involved in regulating mood, appetite, and sleep. Dopamine plays a role in reward-motivated behavior and motor control. Endorphins are involved in pain regulation and are often referred to as the body's natural painkillers.

Correct Answer: C

Rationale: The simple columnar epithelium lining the small intestine is crucial for absorption. This type of epithelium is specialized for absorption due to its tall and closely packed cells, which increase the surface area available for nutrient absorption. The primary function of the small intestine is to absorb nutrients from digested food, and the simple columnar epithelium's structure aids in this process by providing a large surface area for absorption. Choices A, B, and D are incorrect because movement, support, and insulation are not primary functions associated with the simple columnar epithelium in the small intestine. While these functions are essential in other tissues or organs, absorption is the key role of the simple columnar epithelium in the small intestine.

Correct Answer: D

Rationale: The Golgi apparatus is responsible for the final stages of protein modification and packaging for secretion in animal cells. After proteins are synthesized in the rough endoplasmic reticulum (RER), they are transported to the Golgi apparatus for further processing, sorting, and packaging before being sent to their final destination within or outside the cell. The smooth endoplasmic reticulum (SER) is mainly involved in lipid metabolism and detoxification processes, not protein modification. Ribosomes are the cellular organelles responsible for protein synthesis, not the final stages of protein modification and packaging for secretion, which is the role of the Golgi apparatus.

Correct Answer: B

Rationale: The correct characteristic property of acids is a sour taste. Acids release hydrogen ions when dissolved in water, giving them a sour taste. Bitter taste is a property associated with bases, not acids. Slippery feel is a characteristic property of bases, due to their soap-like nature. Sweet taste does not accurately describe the characteristic property of acids, as they are known for their sour taste.

Correct Answer: C

Rationale: The correct answer is C: Somatic nervous system. The major divisions of the nervous system are the central nervous system, which includes the brain and spinal cord, and the peripheral nervous system, which includes all the nerves outside of the central nervous system. The somatic nervous system, which controls voluntary movements and reflexes, is a part of the peripheral nervous system. The autonomic nervous system is another subdivision of the peripheral nervous system that regulates involuntary functions like heart rate and digestion. Therefore, the somatic nervous system is not a major division of the nervous system, making it the correct answer.