Keratomalacia is:

Correct Answer: B

Rationale: The correct answer is B because keratomalacia is specifically defined as softening and subsequent ulceration and perforation of the cornea due to severe vitamin A deficiency. Choice A is incorrect as it describes xerophthalmia, not keratomalacia. Choice C describes photophobia, not keratomalacia. Choice D is incorrect as it includes all the options, but only choice B accurately defines keratomalacia.

Correct Answer: D

Rationale: The correct answer is D because the parathyroid hormone (PTH) has multiple functions in the body. A: PTH increases calcium and phosphate absorption in the intestine by stimulating the production of active vitamin D. B: PTH decreases calcium excretion and increases phosphate excretion in the kidneys, helping to maintain serum calcium levels. C: In bone, PTH increases calcium and phosphate resorption at high doses and may increase bone formation at low doses. Therefore, all of the above statements are true, making D the correct choice.

Correct Answer: A

Rationale: The correct answer is A: Calcium carbonate. It is often the preparation of choice due to its high calcium content (40%). This means that a smaller dose can provide the required amount of elemental calcium compared to other options. Additionally, calcium carbonate is well-absorbed in an acidic environment, making it suitable for individuals with normal gastric acid production. Incorrect choices: B: Calcium lactate has a lower calcium content (13%) compared to calcium carbonate, requiring a higher dose to achieve the same calcium intake. C: Calcium phosphate has a lower calcium content (25%) compared to calcium carbonate, making it less efficient in providing elemental calcium. D: Calcium citrate has a lower calcium content (17%) compared to calcium carbonate and is better absorbed in individuals with low gastric acid production. However, in general, calcium carbonate is preferred for its higher calcium content and cost-effectiveness.

Correct Answer: A

Rationale: Acetazolamide inhibits carbonic anhydrase in the proximal convoluted tubule, leading to decreased bicarbonate reabsorption and subsequent diuresis. This mechanism occurs at the site of action for the drug, making choice A the correct answer. Choices B, C, and D are incorrect because acetazolamide does not act directly at these sites within the nephron.

Correct Answer: C

Rationale: The correct answer is C: Amphotericin B. Amphotericin B is an antifungal medication used for systemic and deep mycotic infections due to its broad spectrum and effectiveness. It works by binding to ergosterol in the fungal cell membrane, leading to cell membrane disruption. Co-trimoxazole (A) is an antibiotic used for bacterial infections. Griseofulvin (B) is used for superficial fungal infections like ringworm. Nitrofungin (D) is an antifungal medication used for topical treatment. Therefore, Amphotericin B is the most appropriate choice for systemic and deep mycotic infections.