Correct Answer: C

Rationale: Ptosis (drooping eyelid) and diplopia (double vision) are classic symptoms of myasthenia gravis. Muscle atrophy (Choice A) is not a typical early manifestation of myasthenia gravis. While facial weakness (Choice B) can occur, it is not as specific as ptosis and diplopia. Increased muscle tone (Choice D) is more indicative of conditions like spasticity, not myasthenia gravis.

Correct Answer: B

Rationale: The correct answer is B: Candida albicans. Candida albicans is a common fungal agent responsible for causing vaginal yeast infections characterized by itching and burning. It is known to overgrow in the vagina, especially when the normal vaginal flora is disrupted, such as during antibiotic use. Cryptococcus neoformans is more associated with causing meningitis in immunocompromised individuals, not vaginal symptoms. Aspergillus is more commonly associated with lung infections and allergic reactions, not vaginal infections. Dermatophytes typically cause skin infections like ringworm, not vaginal symptoms.

Correct Answer: C

Rationale: Ivermectin (Stromectol) is commonly used to treat parasitic infections, particularly Strongyloides stercoralis. This parasitic infection is known to respond well to Ivermectin therapy. Entamoeba histolytica causes amoebiasis and is typically treated with antiprotozoal drugs like metronidazole, not Ivermectin. Giardia lamblia is a protozoan parasite causing giardiasis, which is usually treated with medications like metronidazole or tinidazole, not Ivermectin. Plasmodium falciparum is a malaria-causing parasite and is not treated with Ivermectin but with antimalarial medications like chloroquine or artemisinin-based combination therapies.

Correct Answer: A

Rationale: The correct answer is A: Blood. IgA1 is mainly found in the blood and plays a crucial role in preventing infections by neutralizing pathogens. While IgA1 can be present in other body areas, its primary function is associated with preventing infections in the blood. Choices B, C, and D are incorrect as IgA1 is not primarily associated with the kidneys, lungs, or mucous membranes.

Correct Answer: A

Rationale: An attenuated antigen used in a vaccine is alive but less infectious, aiming to stimulate an immune response. Choice B is incorrect because an attenuated antigen is not highly infectious. Choice C is incorrect as the antigen is intentionally altered to be less infectious. Choice D is incorrect as an attenuated antigen is not infectious.