Indication of vitamin D3 is:

Correct Answer: D

Rationale: The correct answer is D: Osteomalacia. Vitamin D3 is indicated for the treatment of osteomalacia, a condition characterized by softening of the bones due to a deficiency of vitamin D. It helps in the absorption of calcium and phosphorus, leading to proper bone mineralization. A: Hypercalcemia is not an indication for vitamin D3 as it can worsen the condition by increasing calcium levels further. B: Paget's disease is not a primary indication for vitamin D3 therapy. Treatment usually involves bisphosphonates. C: Hypophosphatemia is a condition where there is low phosphate levels, and treatment involves phosphate supplementation, not just vitamin D3.

Correct Answer: A

Rationale: The correct answer is A: TRUE. Some microorganisms can indeed develop alternative metabolic pathways to bypass the inhibition caused by a drug. This is a common phenomenon known as drug resistance in microbial populations. Other choices are incorrect: B is false because drug resistance through alternative pathways is a known fact; C (All) is incorrect as not all microorganisms exhibit this behavior; and D (None) is incorrect as some microorganisms do develop alternative pathways to counter drug inhibition.

Correct Answer: B

Rationale: The correct answer is B: Inhibition of dihydropteroate synthase. Sulfonamides work by inhibiting dihydropteroate synthase, an enzyme involved in the folate synthesis pathway in bacteria. This disruption leads to a decrease in production of essential nucleotides, ultimately inhibiting bacterial growth. A: Inhibition of dihydropteroate reductase is incorrect as sulfonamides target dihydropteroate synthase, not reductase. C: Inhibition of cyclooxygenase is incorrect as this mechanism is related to NSAIDs, not sulfonamides. D: Activation of DNA gyrase is incorrect as this mechanism is associated with antibiotics like fluoroquinolones, not sulfonamides.

Correct Answer: A

Rationale: The correct answer is A: Metronidazole and diloxanide. Metronidazole is effective against the invasive form of Entamoeba histolytica, the parasite causing amebiasis. Diloxanide is used to eliminate the non-invasive cyst form of the parasite in the intestine. Streptomycin (choice B) is not effective against amebiasis. Iodoquinol (choice C) is used for non-invasive amebiasis but not the intestinal form. Emetine (choice D) is reserved for extraintestinal disease and is not commonly used due to its toxicity.

Correct Answer: B

Rationale: Fluorouracil is an antimetabolite that interferes with DNA and RNA synthesis. It is used to treat various cancers by inhibiting cell growth. This makes option B the correct choice. Antibiotics (A) target bacteria, not cancer cells. Plant alkaloids (C) are derived from plants and have different mechanisms of action. Bone marrow growth factors (D) stimulate the production of blood cells but do not directly inhibit cancer cell growth.