In the presence of antidiuretic hormone (ADH), or vasopressin, water is mostly reabsorbed in the ___________ of the nephron.

Correct Answer: A

Rationale: The correct answer is A: Proximal convoluted tubule. ADH acts on the collecting duct and distal convoluted tubule to increase water reabsorption. However, the majority of water reabsorption occurs in the proximal convoluted tubule due to its high permeability to water. This segment reabsorbs about 65% of filtered water, mainly through osmosis. The loop of Henle plays a crucial role in concentrating urine, but it is not the main site of water reabsorption. The collecting duct responds to ADH but reabsorbs a smaller fraction of filtered water compared to the proximal tubule. The distal convoluted tubule is primarily involved in electrolyte reabsorption rather than water reabsorption.

Correct Answer: B

Rationale: Step-by-step rationale for why Nystatin is the correct choice for monilial diarrhea: 1. Nystatin is an antifungal medication specifically effective against Candida species causing monilial infections. 2. It works by binding to ergosterol in fungal cell membranes, disrupting membrane integrity and causing cell death. 3. Nystatin is not absorbed systemically, making it suitable for gastrointestinal infections. 4. Amphothericin B is reserved for severe systemic fungal infections due to its significant toxicity. Ketoconazole and Itraconazole are not typically used for gastrointestinal Candida infections, as they are more commonly used for systemic fungal infections.

Correct Answer: D

Rationale: Step-by-step rationale: 1. Chloramphenicol is effective in curing typhoid fever by targeting the bacteria causing the infection. 2. However, chloramphenicol does not effectively eradicate the bacteria from the carrier state. 3. Ceftriaxone, ciprofloxacin, and cotrimoxazole are also effective in treating typhoid fever but do not specifically target the carrier state. 4. Therefore, the correct answer is D, Chloramphenicol, as it cures typhoid fever but does not prevent the carrier state.

Correct Answer: B

Rationale: The correct answer is B: Cefuroxime. Cefuroxime is a second-generation cephalosporin that has demonstrated in vitro activity against anaerobic gram-negative bacteria like Bacteroides fragilis. This is due to its broader spectrum of activity compared to other choices. A: Cefdinir is a third-generation cephalosporin with limited activity against anaerobic gram-negative bacteria. C: Cefazolin is a first-generation cephalosporin primarily effective against aerobic gram-positive bacteria. D: Cefepime is a fourth-generation cephalosporin with limited activity against anaerobic gram-negative bacteria.

Correct Answer: D

Rationale: The correct answer is D because both Ganciclovir and Foscarnet are active against cytomegalovirus (CMV). Ganciclovir works by inhibiting viral DNA polymerase, while Foscarnet inhibits viral DNA polymerase and reverse transcriptase. Acyclovir, on the other hand, is not effective against CMV as it primarily targets herpes simplex virus and varicella-zoster virus. Therefore, choices A and B are correct for CMV treatment, making option D the correct answer.