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: Dental
The best pickling solution for gypsum bonded investment is: 
Select and explain. 
A. Hydrochloric acid, B. Nitric acid, C. Sulphuric acid, D. Phosphoric acid
A: Hydrochloric acid
Answer: A: Hydrochloric acid 
Explanation: None