Correct Answer: B

Rationale: The correct answer is B: 'Use of nitrates.' Sildenafil (Viagra) is contraindicated in patients taking nitrates due to the risk of severe hypotension. Nitrates and sildenafil both cause vasodilation, and their combined use can lead to a dangerous drop in blood pressure. Choices A, C, and D are incorrect because a history of hypertension, recent use of antihypertensive medications, or a history of peptic ulcer disease are not direct contraindications for using sildenafil.

Correct Answer: B

Rationale: In an 8-year-old boy with a sex hormone deficiency being treated with testosterone, the appearance of signs of puberty would necessitate stopping the treatment. Testosterone therapy in this case aims to supplement the deficient sex hormones but should not trigger premature puberty. Excessive growth in height (choice A) is not a typical reason to stop testosterone therapy. Recurrent urinary tract infections (choice C) and increased blood pressure (choice D) are not directly related to testosterone therapy in this context.

Correct Answer: A

Rationale: The correct instruction is to apply testosterone gel after showering and allow it to dry completely before dressing. This helps prevent the transfer of the gel to others and ensures proper absorption. Choice B is incorrect because the gel should not be applied to the genitals. Choice C is incorrect as there is no specific benefit to applying the gel before bedtime. Choice D is incorrect as the gel should not be applied to the face and neck for the treatment of hypogonadism.

Correct Answer: D

Rationale: The correct answer is D: B and T cell deficits. Severe combined immune deficiency (SCID) syndrome affects both B and T cells, leading to a severe impairment in the immune system's ability to fight infections. Choice A (B cell deficits) is incorrect because SCID affects not only B cells but also T cells. Choice B (T cell deficits) is incorrect as SCID is characterized by deficits in both B and T cells. Choice C (Complement deficits) is incorrect as SCID primarily involves B and T cell deficiencies rather than complement deficiencies.

Correct Answer: B

Rationale: The correct answer is B: 'Use of nitrates.' Sildenafil (Viagra) is contraindicated in patients taking nitrates due to the risk of severe hypotension. Nitrates and sildenafil both cause vasodilation, and their combined use can lead to a dangerous drop in blood pressure. Choices A, C, and D are incorrect because a history of hypertension, recent use of antihypertensive medications, or a history of peptic ulcer disease are not direct contraindications for using sildenafil.