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
Cholera toxin – 
Select and explain. 
A. increase the levels of intracellular cyclic GMP, B. Act through opiate receptor, C. causes continued activation of adenyl cyclase, D. inhibit the enzyme phosphodiesterase
C: causes continued activation of adenyl cyclase
Answer: C: causes continued activation of adenyl cyclase 
Explanation: None