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: Surgery
There was a sudden increases in the size of thyroid swelling along with pain. Most likely cause is ? 
Select and explain. 
A. Hemorrhage within the cyst (Thyroid), B. Malignant change, C. Nodular goiter, D. Colloid goiter
A: Hemorrhage within the cyst (Thyroid)
Answer: A: Hemorrhage within the cyst (Thyroid) 
Explanation: Ans. is 'a' i.e., Hemorrhage within the cyst (thyroid)