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: None