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
The most common cause of hypehyroidism is: 
Select and explain. 
A. Thyroid hyperplasia, B. Thyroid adenoma, C. Thyroid carcinoma, D. Grave disease
D: Grave disease
Answer: D: Grave disease 
Explanation: Answer is D (Grave's Disease): Grave's disease is the single most common cause for Hypehyroidism and Thyrotoxicosis.