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: Medicine
A 64 year old lady Kamla complains of severe unilateral headache on the right side and blindness for 2 years. On examination there is a thick cord like structure on the lateral side of the head. The ESR is 80 mm/hr in the first hour. The most likely diagnosis is - 
Select and explain. 
A. Temporal arteritis, B. Migraine, C. Cluster headache, D. Sinusitis
A: Temporal arteritis
Answer: A: Temporal arteritis 
Explanation: None