Correct Answer: A

Rationale: The correct answer is A: Nystatin. Nystatin is specifically used to treat intestinal candidiasis because it targets and eliminates the Candida species responsible for the infection. It is not absorbed systemically, acting only locally in the gastrointestinal tract. Griseofulvin (B) is mainly used to treat fungal skin infections, not intestinal candidiasis. Undecyne (C) is an antifungal agent used for skin infections, not for intestinal candidiasis. Amphotericin B (D) is a potent antifungal agent used for systemic fungal infections, not specifically for intestinal candidiasis.

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is a Gram-positive cocci that often appear in pairs and can have a capsule. It is a common cause of sore throat and fever, known as streptococcal pharyngitis. Staphylococcus aureus (B) is a Gram-positive cocci but does not typically form pairs. Neisseria meningitidis (C) is a Gram-negative diplococcus and is more associated with meningitis. Klebsiella pneumoniae (D) is a Gram-negative rod and not typically associated with sore throat and fever.

Correct Answer: D

Rationale: The correct answer is D: Amebiasis. The patient's symptoms of gastrointestinal disturbance and liver abscess are indicative of an infection with Entamoeba histolytica, the protozoan parasite responsible for amebiasis. The patient's travel history to an African country also increases the likelihood of contracting this disease, as it is more prevalent in tropical regions. Toxoplasmosis (A) is primarily associated with exposure to cat feces, Leishmaniasis (B) is transmitted through sandfly bites, and Malaria (C) is caused by Plasmodium parasites transmitted through mosquito bites. Therefore, these options are incorrect given the patient's presentation and travel history.

Correct Answer: B

Rationale: The correct answer is B: Insect. A vehicle transmission refers to the mode by which a disease spreads from one host to another. Insects can transmit diseases, making them a vehicle for transmission. Airborne, foodborne, and bodily fluid transmissions are well-known modes of disease spread, while insects are also known vectors for diseases like malaria and Zika.

Correct Answer: A

Rationale: The correct answer is A: Immobilization. This technique is called the Treponema pallidum immobilization (TPI) test, used to diagnose syphilis. The rationale is as follows: 1. TPI test detects antibodies that prevent the movement of treponemas, causing their death. 2. By immobilizing the treponemas, it indicates the presence of specific antibodies against syphilis. 3. This test is highly specific for syphilis diagnosis as it directly targets the causative agent. Other choices are incorrect: B: Complement binding - Not specific to syphilis, more commonly used for other diseases. C: Agglutination - Detects clumping of particles, not specific to treponemas or syphilis. D: Precipitation - Involves the formation of a solid, not directly related to treponema movement or death.