Correct Answer: A

Rationale: The correct order of some of the vertebrae in the human skeleton in descending order is Atlas, Axis, Thoracic, Lumbar, Sacral, Coccyx. This sequence follows the typical arrangement from the top of the spine down towards the pelvis. Choice B is incorrect as it does not follow the descending order of vertebrae. Choice C is incorrect as it starts with Thoracic which is not the first vertebra in the descending order. Choice D is incorrect as it starts with Coccyx which is the last vertebra in the descending order.

Correct Answer: A

Rationale: The statement 'Digestion of starch begins in the mouth' is correct. Salivary amylase, an enzyme produced in the salivary glands, initiates the breakdown of starch into simpler sugars like maltose in the mouth before further digestion in the stomach. This initial breakdown of starch is crucial in the digestion of carbohydrates, marking the beginning of the digestive process. Choice B is incorrect because amylase is produced in the salivary glands, not the stomach. Choice C is incorrect because di- and tri-saccharides are further broken down into monosaccharides before absorption. Choice D is incorrect because proteases are enzymes that break down proteins, not starches.

Correct Answer: D

Rationale: In the context of genetics, genotype refers to an individual's genetic makeup, while phenotype refers to the observable characteristics resulting from the interaction of the genotype with the environment. Red hair and a height of six feet are observable characteristics, making them part of the individual's phenotype. Therefore, both red hair and height are aspects of the individual's phenotype. Choices A and B are incorrect as they incorrectly assign one characteristic to the genotype and the other to the phenotype, which is not accurate. Choice C is incorrect as it states that both characteristics describe the genotype, which is inaccurate as they are observable traits. The correct answer is D, as both red hair and height are observable traits or characteristics, falling under the definition of phenotype in genetics.

Correct Answer: D

Rationale: The correct answer is D: Stomach. The stomach is an organ of the digestive system. Its main function is to break down and digest food, allowing the nutrients to be absorbed into the body. The stomach secretes digestive enzymes and acids to help in the digestion process. Choices A, B, and C are incorrect as the spine, lungs, and brain are not part of the digestive system. The spine is part of the skeletal system, the lungs belong to the respiratory system, and the brain is part of the nervous system.

Correct Answer: B

Rationale: The correct answer is the axon. The axon is the elongated, threadlike part of a neuron that carries nerve impulses away from the cell body towards other neurons or target cells, such as muscles or glands, in the direction of a synapse. Action potentials travel along the axon as electrical signals to communicate with neighboring cells. The cell body (choice A) contains the nucleus and organelles but does not transmit action potentials. Neuron (choice C) is a broad term that includes the entire nerve cell, not a specific structure. Myelin (choice D) is a fatty substance that surrounds and insulates axons, aiding in the conduction of nerve impulses, but it does not directly carry the action potential towards a synapse.