This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ear, Subject name: ENT
[{'content': 'Ca Wheel sign is seen in \nSelect and explain. \nA. ASOM, B. AOM, C. OME, D. CSOM', 'role': 'user'}, {'content': 'Answer: A \nExplanation: In a stage of pre-suppuration of ASOM, there is congestion of pars tensa. A leash of blood vessels appears along with the handle of malleus and at the periphery of tympanic membrane impaing it a ca-wheel appearance. Later, whole tympanic membrane including pars flaccid becomes uniformly red. Ref: Textbook of diseases of ENT, PL Dhingra, 7th edition, pg no. 67', 'role': 'assistant'}]