Correct Answer: D

Rationale: The correct answer is D: Erysipeloid. Erysipeloid is a bacterial infection caused by Erysipelothrix rhusiopathiae commonly found in animals like cattle. The patient's occupation as a cattle-ranch worker puts them at risk for this infection. Symptoms such as high body temperature, severe headache, carbuncle on the forearm with edema, and regional lymphadenitis are typical of erysipeloid. Anthrax (A) is more associated with skin lesions and severe systemic symptoms. Carcinoma of skin (B) presents differently with slow-growing skin lesions. Erysipelas (C) is a different bacterial infection characterized by red, swollen patches on the skin.

Correct Answer: D

Rationale: The correct answer is D: III, IV, V. 1. RNA viruses belong to Group III of the Baltimore classification system because their genetic material is single-stranded RNA. 2. They are also categorized under Group IV as they use reverse transcriptase to replicate their genetic material. 3. Finally, RNA viruses fall under Group V as they have an envelope derived from the host cell membrane. Therefore, options A, B, and C are incorrect as they do not include all the correct groups that RNA viruses belong to according to the Baltimore classification system.

Correct Answer: C

Rationale: To calculate the total magnification, we multiply the magnification of the ocular lens by the magnification of the objective lens. In this case, 10 (ocular) x 40 (objective) = 400. This is why choice C (400) is correct. Choices A, B, and D are incorrect because they do not represent the correct calculation of total magnification based on the given magnification powers of the ocular and objective lenses.

Correct Answer: C

Rationale: The correct answer is C: Bacillus subtilis. Bacillus subtilis is known for its spore-forming ability, which is a survival mechanism to withstand harsh conditions. Spore formation allows the bacteria to become dormant and resistant to heat, chemicals, and radiation. Escherichia coli (A) is not known for spore formation. Staphylococcus aureus (B) does not form spores either. Listeria monocytogenes (D) is a pathogenic bacterium but does not typically form spores.

Correct Answer: A

Rationale: The correct answer is A: Rifampicin. Rifampicin can cause red-orange discoloration of bodily fluids like urine due to its metabolism. This phenomenon is harmless but alarming to patients. Isoniazid (B) can cause peripheral neuropathy, Pyrazinamide (C) can cause hyperuricemia, and Ethambutol (D) can cause optic neuropathy.