This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Pharmacology
[{'content': 'Sildenafil acts by - \nSelect and explain. \nA. Increasing cGMP, B. Decreasing cGMP, C. Increasing cAmp, D. Decreasing cAmp', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Increasing cGMP * Sildenafil has been explained in previous sessions", 'role': 'assistant'}]