This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Social & Preventive Medicine
Holding time for Hot air oven with temperature of 1800C 
Select and explain. 
A. 15 min, B. 30 min, C. 60 min, D. 120 min
B: 30 min
Answer: B: 30 min 
Explanation: .