The first physical sign associated with puberty in boys is:

Correct Answer: E

Rationale: I'm sorry, but it seems there might be a mistake in the question as there is no option E provided. However, I can provide a rationale for each option based on the typical sequence of physical changes during puberty in boys. The first physical sign associated with puberty in boys is usually pubic hair development (D), followed by penis lengthening (B), height spurt (A), and lastly sperm production (C). Pubic hair development is often the initial visible sign of puberty due to hormonal changes. Height spurt and penis lengthening occur later in puberty, while sperm production typically begins towards the end of puberty.

Correct Answer: A

Rationale: The correct answer is A: Vancomycin. Red man syndrome is a type of hypersensitivity reaction associated with rapid intravenous infusion of vancomycin. This is due to the release of histamine from mast cells and basophils. Vancomycin is known to cause this syndrome, while the other antibiotics listed do not have a similar association. Clindamycin is more commonly associated with pseudomembranous colitis, Cefoperazone with liver toxicity, and Piperacillin with hypersensitivity reactions like rash or anaphylaxis. Therefore, based on the mechanism of action and clinical evidence, vancomycin is the correct choice for causing red man syndrome.

Correct Answer: A

Rationale: The correct answer is A: Dapsone. Dapsone is known to cause hemolysis in patients with G6PD deficiency due to oxidative stress. G6PD deficiency leads to reduced ability to protect red blood cells from oxidative damage, which can be exacerbated by drugs like dapsone. Rifampicin and clofazimine are not associated with hemolysis in G6PD deficient patients. Option D is incorrect as dapsone is known to cause hemolysis in this population.

Correct Answer: D

Rationale: The correct answer is D: Clindamycin. Clindamycin is associated with the highest incidence of antibiotic-associated pseudomembranous enterocolitis due to its broad-spectrum activity that disrupts the normal gut flora, leading to overgrowth of Clostridium difficile. Ampicillin, Chloramphenicol, and Vancomycin are also associated with pseudomembranous enterocolitis, but the highest incidence is seen with Clindamycin due to its stronger impact on gut flora imbalance.

Correct Answer: B

Rationale: The correct answer is B. Nevirapine has a higher risk of severe hepatotoxicity in patients with higher CD4 cell counts. Choice B specifies a lower threshold for CD4 cell counts in women compared to men, which aligns with the caution needed for initiating Nevirapine. Choices A, C, and D have higher CD4 cell count thresholds for both women and men, which would increase the risk of hepatotoxicity if Nevirapine is initiated in those patients. Therefore, Choice B is the most appropriate option to minimize the risk of hepatotoxicity when initiating Nevirapine.