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
Most common cause of Thyroiditis is: 
Select and explain. 
A. Reidl 's Thyroiditis, B. Subacute Thyroditis, C. Hashimoto's Thyroiditis, D. Viral Thyroiditis
C: Hashimoto's Thyroiditis
Answer: C: Hashimoto's Thyroiditis 
Explanation: Answer is C (Hashimoto's Thyroiditis) Hashimotas thyroiditis, also called chronic lymphocytic thyroiditis, is the most common firm of thyroiditis.