Correct Answer: A

Rationale: The correct answer is A: Erythrocytic schizogony. In this case, the patient most likely has malaria, specifically caused by Plasmodium falciparum. The fever attacks every 2 days (tertian fever) are characteristic of P. falciparum infection. The cycle of erythrocytic schizogony in P. falciparum is around 48 hours, leading to the recurring fever pattern. Choices B, C, and D are incorrect as tissue schizogony does not cause the characteristic fever pattern, exotoxins are not typically involved in malaria fever, and gametocytes do not directly cause fever attacks.

Correct Answer: A

Rationale: The correct answer is A: Entamoeba histolytica. This protozoon is responsible for causing amoebic dysentery, which presents with bloody diarrhea. The "raspberry jelly" appearance of stool is due to the presence of mucosal lining and blood. The large mononuclear cells with absorbed red blood cells are characteristic of the histopathology of Entamoeba histolytica infection. Giardia lamblia (B) causes watery diarrhea, not bloody stools. Campylobacter jejuni (C) is a bacterial pathogen associated with gastroenteritis, but does not typically cause bloody diarrhea. Toxoplasma gondii (D) causes toxoplasmosis, a systemic infection with symptoms such as fever and lymphadenopathy, but not bloody diarrhea.

Correct Answer: A

Rationale: The correct answer is A: Leptospira. Leptospira is a spiral-shaped bacterium that causes a disease known as leptospirosis, characterized by fever, jajsondice, hemorrhagic rash, and renal insufficiency. The characteristic spiral shape of the bacteria, resembling 'C' and 'S' letters, is a key identifying feature. Leptospira is commonly associated with contaminated water sources and can be transmitted to humans through contact with infected animals or water. Summary of other choices: B: Treponema - Treponema pallidum is the causative agent of syphilis, which does not typically present with the combination of symptoms described in the question. C: Borrelia - Borrelia species are associated with Lyme disease and relapsing fever, but do not match the specific symptoms and histological appearance described in the question. D: Spirochaeta - Spirochaeta is a genus of bacteria, but specific species within

Correct Answer: A

Rationale: The correct answer is A: Streptococcus pneumoniae. This bacterium is the most common cause of bacterial pneumonia in adults. It is a leading cause of community-acquired pneumonia. Streptococcus pneumoniae is known for its ability to infect the respiratory tract and cause inflammation in the lungs leading to pneumonia. Mycobacterium tuberculosis causes tuberculosis, not pneumonia. Escherichia coli is associated with urinary tract infections and gastrointestinal illnesses, not pneumonia. Clostridium botulinum causes botulism, a severe form of food poisoning, but not pneumonia. Therefore, the correct choice is Streptococcus pneumoniae as it is specifically known for causing pneumonia.

Correct Answer: D

Rationale: Step-by-step rationale: 1. The study results indicate water contamination. 2. Contaminated water poses health risks. 3. Therefore, the correct interpretation is that water is contaminated. Summary: - Choice A is incorrect as safety is not confirmed. - Choice B is too mild given the severity of contamination. - Choice C is also incorrect, as it does not accurately reflect the study findings.