Ingestion of polar bear liver may cause acute poisoning of:

Correct Answer: C

Rationale: Step-by-step rationale: 1. Polar bear liver contains high levels of Vitamin A. 2. Excessive Vitamin A intake can lead to acute poisoning. 3. Symptoms of Vitamin A poisoning include nausea, vomiting, dizziness, and even death. 4. Thus, ingestion of polar bear liver can cause acute poisoning due to Vitamin A overload. Summary: A: Vitamin D - Incorrect. Polar bear liver does not contain toxic levels of Vitamin D. B: Vitamin E - Incorrect. Vitamin E toxicity is rare and not associated with polar bear liver ingestion. C: Vitamin A - Correct. Polar bear liver is high in Vitamin A, leading to acute poisoning if consumed in excess. D: Vitamin C - Incorrect. Vitamin C toxicity is unlikely from consuming polar bear liver.

Correct Answer: C

Rationale: Rationale: 1. Both Doxercalciferol (Hectoral) and Paricalcitol (Zemplar) are synthetic analogs of 1,25-dihydroxyvitamin D3. 2. Doxercalciferol is converted to calcitriol in the body. 3. Paricalcitol is a selective vitamin D receptor activator. Summary: A: Doxercalciferol is correct as it is a synthetic analog of calcitriol. B: Paricalcitol is correct as it is also a synthetic analog of calcitriol. C: Correct as both A and B are true. D: Incorrect as both A and B are commercially available analogs of calcitriol.

Correct Answer: B

Rationale: The correct answer is B: Amiloride (Midamor). It is a potassium-sparing diuretic that blocks Na+ channels in the collecting tubules. Amiloride specifically targets the epithelial sodium channels in the collecting tubules, leading to decreased sodium reabsorption and potassium retention. Acetazolamide (A) is a carbonic anhydrase inhibitor, Furosemide (C) is a loop diuretic that inhibits the Na+-K+-2Cl- symporter, and Hydrochlorothiazide (D) is a thiazide diuretic that inhibits the Na+-Cl- symporter in the distal convoluted tubule.

Correct Answer: B

Rationale: The correct answer is B: Cefaclor. Cefaclor belongs to the cephalosporin class of antibiotics, specifically a second-generation cephalosporin. Cephalosporins are beta-lactam antibiotics that inhibit bacterial cell wall synthesis. Streptomycin (A) is an aminoglycoside antibiotic, Phenoxymethylpenicillin (C) is a penicillin antibiotic, and Erythromycin (D) is a macrolide antibiotic. These choices do not belong to the cephalosporin class.

Correct Answer: D

Rationale: The correct answer is D: Rifampin. Rifampin is an antimycobacterial drug that is commonly used to treat tuberculosis and other mycobacterial infections. It works by inhibiting the RNA polymerase enzyme in mycobacteria, leading to the suppression of bacterial growth. Isoniazid (Choice A) is also used for tuberculosis treatment, but it is not classified as an antibiotic. PAS (Choice B) is an antimycobacterial drug but is not an antibiotic. Ethambutol (Choice C) is also used to treat tuberculosis, but it works by inhibiting cell wall synthesis rather than RNA polymerase. Therefore, the correct choice is Rifampin as it directly targets the mycobacterial RNA polymerase enzyme, making it an effective antibiotic for treating mycobacterial infections.