This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
A common cause of Primary hyperparathyroidism is- 
Select and explain. 
A. Multiple parathyroid adenomas, B. Solitary parathyroid adenoma, C. Solitary thyroid adenoma, D. Ectopic PTH production
B: Solitary parathyroid adenoma
Answer: B: Solitary parathyroid adenoma 
Explanation: a single abnormal parathyroid gland is the cause in 80% of patients ( harre 17 pg 2380)