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
Landmark which is immune to surface deposition and resorption: 
Select and explain. 
A. Xi point and Eva point, B. Point A and Point B, C. Porion and Basion, D. Pogonion and Gnathion
A: Xi point and Eva point
Answer: A: Xi point and Eva point 
Explanation: Arcial growth of mandible: 

Proposed by Ricketts.
The advantage was that the arc of growth can be constructed for every individual depending on the length of the core of the mandible.
In order to locate the central core, which is immune to surface deposition and resorption, he introduced 2 landmarks - Xi point and Eva point on the mandibular ramus.
Xi Point: Represents geometric centre of ramus.
Eva point: In dried mandible, the stress lines run on the medial aspect parallel to the external oblique ridge and ascend up the ramus. The stress lines fork into two at a  particular point that was named as Eva point.

Ref: Shreedhar Premkumar 1st edition P:199