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: Unknown
[{'content': 'Marbling is due to ? \nSelect and explain. \nA. Veins becoming visible due to decomposition of blood, B. Clotting ofblood in veins, C. Lightening, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans-A', 'role': 'assistant'}]