Correct Answer: B

Rationale: The correct answer is B: 'Use of nitrates.' Tadalafil (Cialis) is contraindicated in patients taking nitrates due to the risk of severe hypotension. Nitrates and Cialis both cause vasodilation, which can lead to a dangerous drop in blood pressure when used together. Choices A, C, and D are incorrect because a history of hypertension, use of antihypertensive medications, and a history of peptic ulcer disease are not specific contraindications for tadalafil use.

Correct Answer: C

Rationale: The correct answer is C: Impaired arterial blood supply. Dry gangrene is typically caused by impaired arterial blood supply, leading to tissue death without bacterial infection. Choices A, B, and D are incorrect. Inappropriate activation of apoptosis is not a common cause of dry gangrene. Bacterial invasion usually leads to wet gangrene, not dry gangrene. Metaplastic cellular changes are not directly associated with the development of dry gangrene.

Correct Answer: C

Rationale: The correct answer is C: 'A malignant growth of white blood cells.' Leukemia is a type of cancer that affects the blood and bone marrow, leading to an overproduction of abnormal white blood cells. These cells are malignant and impair the normal function of healthy blood cells. Choices A, B, and D are incorrect because leukemia does not involve skin cells or benign growths; instead, it specifically refers to the abnormal proliferation of white blood cells.

Correct Answer: C

Rationale: The correct answer is C: Ischemia. In this scenario, the 75-year-old male experiences chest pain on exertion, which is indicative of angina. Angina is primarily caused by reduced blood flow to the heart muscle, leading to hypoxic injury. This condition is known as ischemia. Options A, B, and D are incorrect. Malnutrition does not typically cause chest pain related to exertion. Free radicals and chemical toxicity are not common causes of chest pain in the context described. Therefore, the most likely cause of chest pain in this case is ischemia due to reduced blood flow.

Correct Answer: A

Rationale: The correct answer is A: "Tamoxifen may increase the risk of venous thromboembolism." It is crucial for patients to be aware of the signs and symptoms of blood clots while taking tamoxifen. Choice B is incorrect because hot flashes and menopausal symptoms are common side effects of tamoxifen, but they are not the key point to emphasize. Choice C is incorrect as weight gain and fluid retention are potential side effects of tamoxifen but not the key point for patient education. Choice D is incorrect as tamoxifen does not decrease the risk of osteoporosis; in fact, it may increase the risk of bone loss.