Correct Answer: A

Rationale: Metformin is classified as an antihyperglycemic agent because it works by reducing hepatic glucose output and decreasing glucose absorption from the gut, thereby preventing hyperglycemia. Choice B, a hypoglycemic agent, is incorrect as hypoglycemic agents stimulate insulin production, which is not the mechanism of action of metformin. Choice C, an insulin analogue, is incorrect as metformin is not a type of insulin but a distinct medication. Choice D, a pancreatic alpha cell stimulant, is incorrect as metformin does not stimulate any pancreatic cells, but rather acts on the liver and gut to lower blood sugar levels.

Correct Answer: C

Rationale: In this scenario, the most appropriate medication to relieve severe ischemic chest pain during a stress test is Procardia. Procardia, a calcium channel blocker, is effective in quickly alleviating chest pain by dilating coronary arteries, improving blood flow to the heart muscle. Aspirin, although important for antiplatelet effects, is not the best choice for immediate relief of severe chest pain. Diazoxide is a vasodilator used in hypertensive emergencies, not for acute chest pain. Mannitol is an osmotic diuretic used to reduce intracranial pressure, not for chest pain relief.

Correct Answer: C

Rationale: The correct answer is 22 gauge. A 22-gauge needle is recommended for school-age children, toddlers, and adolescents due to their muscle mass and tolerance. In infants, a smaller gauge (23-25) is preferred as their muscles are less developed and more sensitive. Choice A, 27 gauge, is too thin for an intramuscular injection in a 12-year-old boy. Choice B, 25 gauge, is more suitable for infants than for a 12-year-old. Choice D, 20 gauge, is too thick and not typically used for intramuscular injections in children.

Correct Answer: D

Rationale: The correct answer is respiratory alkalosis. In respiratory alkalosis, there is an elevated pH and low carbon dioxide levels (PaCO2 < 35 mmHg). In the given arterial blood gas reading, the patient's pH is 7.41 (within normal range), PaCO2 is 29 mmHg (below normal range), indicating respiratory alkalosis. The bicarbonate level is normal (25 mEq/l), ruling out metabolic acidosis or alkalosis. The low PaO2 (54 mmHg) may indicate hypoxemia, but it is not directly related to the acid-base disorder being assessed. Metabolic acidosis (choice A) is characterized by low pH and low bicarbonate levels, which are not present in this case. Respiratory acidosis (choice B) is indicated by low pH and high PaCO2 levels, which also do not match the provided data. Metabolic alkalosis (choice C) is defined by high pH and high bicarbonate levels, which are not seen in this scenario.

Correct Answer: B

Rationale: The correct answer is: 'Larger than normal air spaces and loss of elastic recoil cause air to be trapped in the lung and collapse airways.' Emphysema is a breakdown of the elastin and fiber network of the alveoli where the alveoli enlarge or the walls are destroyed. This alveolar destruction leads to the formation of larger-than-normal air spaces. Emphysema is one of a group of pulmonary diseases of a chronic nature characterized by increased resistance to airflow; the entity is part of chronic obstructive pulmonary disease (COPD). Choice A is incorrect because emphysema is not primarily characterized by hyperactivity of the medium-sized bronchi causing wheezing and tightness in the chest. Choice C is incorrect because vasodilation, congestion, and mucosal edema are not the primary mechanisms involved in emphysema, and they do not directly lead to chronic cough and sputum production. Choice D is incorrect because emphysema is not related to chloride transport issues and thick viscous mucus production.