Propranolol is contraindicated in:

Correct Answer: B

Rationale: Propranolol is a non-selective beta-blocker that can cause bronchoconstriction, making it contraindicated in bronchial asthma. It can worsen asthma symptoms by blocking beta-2 receptors in the lungs. Angina pectoris, hypertension, and arrhythmia are conditions where propranolol is commonly used due to its beta-blocking effects on the heart and blood vessels.

Correct Answer: D

Rationale: The correct answer is D because organophosphate insecticides and nerve gases inhibit acetylcholine metabolism by irreversibly binding to acetylcholinesterase enzyme, leading to accumulation of acetylcholine at synapses. This results in overstimulation of cholinergic receptors, causing symptoms of cholinergic toxicity. Choice A is incorrect because alpha and beta-adrenergic receptors are not the targets of organophosphates. Choice B is incorrect because organophosphates do not block all muscarinic receptors. Choice C is incorrect because organophosphates do not specifically target nicotinic receptors in the brain.

Correct Answer: D

Rationale: The correct answer is D: scurvy. Scurvy is caused by a deficiency of vitamin C, leading to symptoms such as fatigue, bleeding gums, and skin discoloration. Vitamin C is essential for collagen synthesis, and its deficiency impairs collagen formation. A: AIDS is caused by the human immunodeficiency virus (HIV), not by a lack of vitamin C. B: Coronary heart disease is primarily related to factors such as high cholesterol, high blood pressure, and smoking, not vitamin C deficiency. C: Rickets is caused by a deficiency of vitamin D, leading to soft and weak bones, not by a lack of vitamin C.

Correct Answer: D

Rationale: The correct answer is D because lead is the product at the cathode (negative electrode) during electrolysis, while bromine is the product at the anode (positive electrode). Lead is reduced at the cathode to form lead metal, and bromine is oxidized at the anode to form bromine gas. This is in line with the general rule that cations are attracted to the cathode and are reduced, while anions are attracted to the anode and are oxidized. Choice A is incorrect as bromide ions are reduced at the cathode, not lead ions. Choice B is incorrect because bromine is produced at the anode, not lead. Choice C is incorrect because lead ions are reduced at the cathode, not bromide ions.

Correct Answer: D

Rationale: The correct answer is D: solidification. Solidification is the process in which a substance changes from a liquid state to a solid state by losing heat energy. In this process, the particles slow down and come closer together, forming a solid structure. Explanation for why the other choices are incorrect: A: Condensation is the change of state from gas to liquid, not from liquid to solid. B: Evaporation is the change of state from liquid to gas, not from liquid to solid. C: Melting is the change of state from solid to liquid, not from liquid to solid. In summary, the process described in the question, changing from a liquid state to a solid state, is known as solidification, making it the correct answer.