Correct Answer: A

Rationale: The PR interval measures the time it takes for the electrical impulse to travel from the atria to the ventricles. It is crucial in diagnosing heart rhythm disorders, as abnormalities in this interval can indicate conduction abnormalities between the atria and ventricles. Choices B, C, and D are incorrect. The QRS complex represents ventricular depolarization, the QT interval represents the duration of ventricular repolarization, and the ST segment represents the time between ventricular depolarization and repolarization.

Correct Answer: A

Rationale: Mitral regurgitation is the correct answer. It occurs when the mitral valve does not close properly, allowing blood to flow backward into the left atrium. This condition can lead to symptoms such as fatigue, shortness of breath, and if left untreated, it can progress to heart failure. Aortic stenosis (choice B) is a different heart valve condition characterized by narrowing of the aortic valve, restricting blood flow from the heart. Tricuspid regurgitation (choice C) involves the tricuspid valve not closing properly, leading to blood flowing back into the right atrium. Pulmonary hypertension (choice D) is a condition characterized by high blood pressure in the arteries of the lungs.

Correct Answer: B

Rationale: The correct answer is B: Hypokalemia. Furosemide is a loop diuretic that can lead to potassium loss, resulting in hypokalemia. This electrolyte imbalance is a significant risk associated with diuretic use. Choices A, C, and D are incorrect. Hyperkalemia (choice A) is not typically associated with furosemide use. Hyponatremia (choice C) and hypernatremia (choice D) are related to sodium levels, not potassium levels affected by furosemide.

Correct Answer: A

Rationale: The correct answer is A, the carotid body. The carotid body is the major chemoreceptor of the heart responsible for detecting changes in blood oxygen, carbon dioxide, and pH levels. This specialized structure helps regulate the cardiovascular system's response to maintain appropriate oxygen levels in the blood. Choices B, C, and D are incorrect as they are not directly involved in chemoreception in the heart. The aortic body is primarily involved in blood pressure regulation, the vagus nerve is a cranial nerve responsible for parasympathetic innervation, and the SA node is known as the heart's natural pacemaker.

Correct Answer: A

Rationale: Pleural effusion is the correct answer as it refers to the accumulation of excess fluid between the layers of the pleura surrounding the lungs and chest cavity. This condition can be caused by various factors such as infections, heart failure, or cancer. Pulmonary edema (choice B) involves fluid accumulation in the lungs' air sacs and is not specific to the pleura. Atelectasis (choice C) is the collapse or closure of a lung leading to airless lung tissue and is not related to fluid buildup. Sarcoidosis (choice D) is a condition characterized by the growth of tiny collections of inflammatory cells in different parts of the body, not specifically involving fluid accumulation in the pleural space.