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 casting may fail to seat on the prepared tooth due to all of the following factors except _____. 
Select and explain. 
A. Temporary cement still on the prepared tooth after the temporary restoration has been removed., B. Proximal contact(s) of casting too heavy/tight., C. Undercuts present in prepared tooth., D. The occlusal of the prepared tooth was underreduced.
D: The occlusal of the prepared tooth was underreduced.
Answer: D: The occlusal of the prepared tooth was underreduced. 
Explanation: Occlusal reduction would not affect the ability to seat a casting. However, temporary cement, heavy proximal contacts, or tooth undercuts could keep the casting from seating completely.