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: Pharmacology
Drugs like barbiturates precipitate symptoms of porphyria because 
Select and explain. 
A. They depress ALA synthase, B. They inhibit ALA synthase, C. They induce heme oxygenase, D. They inhibit heme oxygenase
A: They depress ALA synthase
Answer: A: They depress ALA synthase 
Explanation: None