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 purpose of plane of orientation is: 
Select and explain. 
A. To serve as a guide in establishing occlusal plane, B. To aid in measuring height and Length of posterior teeth, C. To serve as an arbitrary plane when established on the articulator, D. To divide the distance between upper and Lower cast equally
A: To serve as a guide in establishing occlusal plane
Answer: A: To serve as a guide in establishing occlusal plane 
Explanation: None