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
Toxin acting on cGMP- 
Select and explain. 
A. Heat stable E. coli toxin, B. Heat labile E. coli toxin, C. Cholera toxin, D. Shiga toxin
A: Heat stable E. coli toxin
Answer: A: Heat stable E. coli toxin 
Explanation: Ans. is 'a' i.e., Heat stable E. coli toxin . Cholera toxin (CT) and labile toxin of E.coli (LT) act by activating cAMP. . Stable toxin of E.coli acts by activating cGMP. Remember . Though the mechanism of labile toxin of E.coli (LT) and cholera toxin (CT) is same, cholera toxin is about a hundred times more potent than LT.