This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
True about cholera - 
Select and explain. 
A. Gram negative rod, B. Associated with fever, C. Causes painful watery diarrhea, D. All
A: Gram negative rod
Answer: A: Gram negative rod 
Explanation: Ans. is `a' i.e., Gram negative rod Vibrio cholerae is a gram negative rod (bacillus). It causes painless watery diarrhea, without associated fever. Vibrios are highly susceptible to acids and gastric acidity provides an effective barrier against small dose of V. cholerae. Therefore, achlorhydria predisposes for infection by V cholerae.