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
A rough / chalky surface of the cast is due to all of the following except: 
Select and explain. 
A. Not waiting for 20 min before pouring, B. Excess wetting agent left on impression, C. Air incorporation in the mix, D. Improper powder/water ratio of stone
C: Air incorporation in the mix
Answer: C: Air incorporation in the mix 
Explanation: Air incorporation in the mix leads to bubbles.