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
Median palatal suture is a relief area while making upper edentulous impression  because: 
Select and explain. 
A. It overlies nerves and vessels, B. This area is prone for resorption, C. Overlying mucous membrane is thick, D. The submucosal layer is extremely thin
D: The submucosal layer is extremely thin
Answer: D: The submucosal layer is extremely thin 
Explanation: Maxilla

Supporting structures

Hard palate—rugae
Residual alveolar ridge—maxillary tuberosity


Limiting structures 

Labial frenum
Labial vestibule
Buccal frenum
Buccal vestibule
Hamular notch
Fovea palatine
Posterior palatal seal area


Relief area:

Midpalatine suture
Incisive papilla
Torus palatinus


Stress-bearing areas 

Primary
Horizontal slopes of hard palate lateral to
Median sutures
Secondary
Crest of the residual alveolar ridge
Rugae
Maxillary tuberosity