This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Physiology
In Heme synthesis, which of the following is inhibited by LEAD? 
Select and explain. 
A. Xanthine oxidase, B. ALA dehydratase, C. ALA synthase, D. Uroporphyrin synthase
B: ALA dehydratase
Answer: B: ALA dehydratase 
Explanation: Lead inhibits ALA dehydratase and ferrochelatase, preventing incorporation of iron and causing anemia and porphyria.