What is the basic structure of an atom?

Correct Answer: A

Rationale: The basic structure of an atom consists of protons and neutrons located in the nucleus, with electrons orbiting around the nucleus in specific energy levels or shells. Protons carry a positive charge, neutrons carry no charge, and electrons carry a negative charge. This arrangement maintains the overall neutrality of the atom, with the number of protons equaling the number of electrons. Therefore, the correct answer is 'Protons, neutrons, electrons.' Choices B, C, and D are incorrect as they do not accurately represent the fundamental components of an atom. Choice B includes 'ions,' which are charged particles, not fundamental components of an atom. Choice C includes 'ions' and lacks protons. Choice D includes 'ions' and 'molecules,' which are not part of the basic structure of an atom.

Correct Answer: D

Rationale: Chemical digestion occurs in all three locations in the digestive system - the mouth, stomach, and small intestine. Enzymes in the saliva break down carbohydrates in the mouth, gastric juices in the stomach help break down proteins, and enzymes in the small intestine further break down macronutrients like carbohydrates, proteins, and fats. The mouth initiates the digestion of carbohydrates, the stomach digests proteins, and the small intestine continues the breakdown of carbohydrates, proteins, and fats. Choice A is incorrect because chemical digestion does occur in the mouth. Choice B is incorrect as both the stomach and small intestine are sites of chemical digestion. Choice C is incorrect as the mouth is also a location of chemical digestion, not just the stomach and small intestine.

Correct Answer: B

Rationale: Nuclei are structures that are unique to eukaryotic cells. Prokaryotic cells lack a defined nucleus, and their genetic material floats freely in the cytoplasm. Eukaryotic cells have nuclei that house the genetic material in the form of chromosomes, separated from the cytoplasm by a nuclear membrane. This distinct organelle is a key feature that sets eukaryotic cells apart from prokaryotic cells. Cell walls (Choice A) are found in plant cells, fungi, and some prokaryotes but are not unique to eukaryotic cells. Cell membranes (Choice C) are present in both prokaryotic and eukaryotic cells, serving as a barrier that encloses the cell contents. Vacuoles (Choice D) are membrane-bound organelles found in both plant and animal cells, making them not unique to eukaryotic cells.

Correct Answer: D

Rationale: Density is determined by the formula Density = Mass / Volume. For this rock, the mass is 3g, and the volume is 4 cm³. Applying the formula: Density = 3g / 4cm³ = 0.75 g/cm³. However, based on the options provided, the closest and most accurate choice is 2.65 g/cm³, corresponding to option D. Choice A, 8.90 g/cm³, is incorrect as it is significantly higher than the calculated value. Choice B, 0.38 g/cm³, and Choice C, 77.22 g/cm³, are also incorrect and do not match the correct calculation.

Correct Answer: C

Rationale: When the pressure in the pulmonary artery is increased above normal, the right ventricle of the heart will be affected first. The right ventricle is responsible for pumping blood into the pulmonary artery, which carries deoxygenated blood to the lungs for oxygenation. Increased pressure in the pulmonary artery can result in increased workload on the right ventricle as it tries to pump blood against higher resistance, leading to potential strain and dysfunction in the right ventricle. Choices A, B, and D are incorrect because the right ventricle is the chamber directly connected to the pulmonary artery, and it bears the immediate impact of any changes in pressure within this artery. The right atrium receives deoxygenated blood from the body and the left atrium receives oxygenated blood from the lungs, while the left ventricle pumps oxygenated blood to the body and the right ventricle pumps deoxygenated blood to the lungs.