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: Dental
Porphyrins are synthesized mainly in - 
Select and explain. 
A. Spleen, B. Liver and spleen, C. Bone marrow and spleen, D. Liver and bone marrow
D: Liver and bone marrow
Answer: D: Liver and bone marrow 
Explanation: Porphyrins are synthesized in - Liver, Bone marrow.