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
In the small intestine, cholera toxin acts by- 
Select and explain. 
A. ADP ribosylation of the G regulatory protein, B. Inhibition of adenyl cyclase, C. Activation of GTP ase, D. Active absorption of NaCl
A: ADP ribosylation of the G regulatory protein
Answer: A: ADP ribosylation of the G regulatory protein 
Explanation: None