Route of administration of vitamin D3 is:

Correct Answer: B

Rationale: The correct route of administration for vitamin D3 is oral (Choice B) because it is a fat-soluble vitamin that can be effectively absorbed through the digestive system. Subcutaneous (Choice A) and intravenous (Choice C) routes are not typically used for vitamin D3 as it can lead to potential risks and complications. Intranasal (Choice D) administration is not a common route for vitamin D3 absorption, as it may not provide adequate bioavailability compared to oral ingestion. Therefore, the oral route is the most appropriate and efficient method for administering vitamin D3.

Correct Answer: D

Rationale: Rationale: 1. Choice A is correct because combining antimicrobial agents can enhance their effectiveness against resistant strains. 2. Choice B is correct because a combination can target a wider range of microorganisms. 3. Choice C is correct because using a combination can help reduce the chance of resistance developing. Summary: All of the above choices are correct because rational antimicrobial combinations provide synergism, broad coverage, and prevent resistance emergence.

Correct Answer: C

Rationale: The correct answer is C: "Does not demonstrate nephrotoxicity." Amphotericin B is known for its nephrotoxicity, which can lead to kidney damage. This is a well-documented side effect of the drug. Choices A, B, and D are incorrect because Amphotericin B is indeed used for systemic mycosis treatment, poorly absorbed from the gastrointestinal tract, and influences the permeability of fungus cell membrane, making them true characteristics of the drug.

Correct Answer: B

Rationale: Step 1: Tetracyclins are known to have antimalarial properties by inhibiting protein synthesis in Plasmodium species. Step 2: Aminoglycosides (choice A) primarily target bacteria, not parasites like malaria. Step 3: Carbapenems (choice C) and Penicillins (choice D) are both beta-lactam antibiotics that have no significant antimalarial effects. Summary: Tetracyclins are the correct choice as they directly target malaria parasites, while the other options do not possess antimalarial properties.

Correct Answer: B

Rationale: Methotrexate is a folic acid antagonist. It inhibits dihydrofolate reductase, leading to decreased DNA synthesis. This action makes it effective in treating cancer and autoimmune diseases. Purine antagonists target purine synthesis, antibiotics act on bacterial growth, and alkylating agents damage DNA to prevent cell division. Methotrexate's mechanism aligns with folic acid antagonism, making option B the correct choice.