Correct Answer: A

Rationale: The correct answer is A: Mycobacterium tuberculosis. This bacteria is responsible for causing tuberculosis because it is the specific pathogen known to infect the lungs and other parts of the body, leading to the disease. Mycobacterium tuberculosis has unique cell wall components that allow it to evade the immune system and survive in the host. Neisseria meningitidis (B) causes meningitis, not tuberculosis. Salmonella enterica (C) causes food poisoning, not tuberculosis. Streptococcus pneumoniae (D) causes pneumonia, not tuberculosis. Therefore, the correct answer is A based on the specific characteristics and pathogenicity of Mycobacterium tuberculosis.

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: A

Rationale: The correct answer is A: Trichomonas tenax. Trichomonas tenax is a flagellated protozoan commonly found in the oral cavity and does not have a cyst stage. This organism typically inhabits the gingival crevices and can be identified in dental plaque samples. Entamoeba gingivalis (B) is an amoeba and does not have flagella. Balantidium coli (C) is a ciliated protozoan that infects the intestines, not the oral cavity. Giardia lamblia (D) is a flagellated protozoan that infects the intestines and has a distinct cyst stage. Therefore, the presence of flagellated protozoa without a cyst stage in dental plaque indicates Trichomonas tenax is likely present.

Correct Answer: B

Rationale: Protein A is a virulence factor specific to Staphylococcus aureus. This protein binds to the Fc region of immunoglobulins, inhibiting opsonization and phagocytosis. Therefore, the correct answer is B. Coagulase negative staphylococcus (choice A) does not produce Protein A. Micrococcus (choice C) is a different genus and does not possess Protein A. Choice D is incorrect because Protein A is indeed found in Staphylococcus aureus.

Correct Answer: C

Rationale: The correct answer is C: bioremediation. Bioremediation is the process of using living organisms to clean up environmental pollution, including industrial wastes. This method utilizes microorganisms, plants, or fungi to break down or neutralize pollutants. Biomining (A) is the process of extracting valuable metals from ores using biological organisms. Biosynthesis (B) refers to the production of complex molecules by living organisms. Bioengineering (D) involves the application of engineering principles to biological systems, not specifically related to cleaning up industrial wastes. Therefore, the most appropriate term for the cleanup of industrial wastes by living organisms is bioremediation.