Correct Answer: A

Rationale: The correct answer is A, 'Physiologic.' Physiologic atrophy is a normal part of development, like the reduction in thymus size during childhood. Pathologic atrophy (choice B) refers to tissue wasting due to disease, not a normal process like the reduction in thymus size. Disuse atrophy (choice C) results from a lack of physical activity or stimulation, which is not the case with thymus size reduction. Neurogenic atrophy (choice D) is caused by damage to or diseases of the nerves supplying the muscles, not related to the thymus size reduction seen in childhood.

Correct Answer: B

Rationale: The correct answer is B because anabolic steroids are indeed universally dangerous, but they pose greater risks to adolescents due to their impact on growth and development. Choice A is incorrect because anabolic steroids do have the potential to build muscle mass, though not to the extent often portrayed in the media. Choice C is incorrect as muscle mass gained from steroid use may persist for a period even after discontinuation. Choice D is incorrect as anabolic steroids can enhance muscle performance initially, though long-term use can have adverse effects on health and not specifically on the ability to perform weight-bearing exercises.

Correct Answer: B

Rationale: In patients with chronic renal failure, especially in older adults, dosages of medications excreted renally need to be adjusted based on kidney function. Acyclovir is primarily eliminated by the kidneys, so in a patient with chronic renal failure, the dose would need to be smaller to prevent drug accumulation and toxicity. Choice A is incorrect because the dose adjustment is more related to the patient's kidney function than the presence of herpes simplex. Choice C is incorrect because the type of herpes infection does not determine the dose adjustment for acyclovir. Choice D is incorrect as the creatinine clearance is a more accurate measure of kidney function compared to creatinine levels.

Correct Answer: B

Rationale: The correct answer is B. The effects of finasteride in treating BPH may take several weeks or months to become noticeable, so patients should be informed about this expected time frame. Choice A is incorrect because finasteride does not cure BPH but helps manage symptoms. Choice C is incorrect as increased hair growth is a side effect of finasteride, not an expected outcome for BPH treatment. Choice D is also incorrect as decreased libido is a potential side effect of finasteride, not an expected outcome for BPH treatment.

Correct Answer: A

Rationale: The correct answer is A: Use of nitrates. Sildenafil (Viagra) is contraindicated in patients taking nitrates due to the risk of severe hypotension. Nitrates and sildenafil both cause vasodilation, so their combined use can lead to a dangerous drop in blood pressure. Choices B, C, and D are incorrect because while a history of hypertension or use of antihypertensive medications may influence treatment decisions, they are not the key contraindication specifically related to sildenafil use.