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: Radiology
Investigation of choice for locating Parathyroid gland: 
Select and explain. 
A. Tc Thallium substraction scan, B. CAT Scan, C. USG, D. Angiography
A: Tc Thallium substraction scan
Answer: A: Tc Thallium substraction scan 
Explanation: A i.e. Tc-Thallium Substraction Scan