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
Record base thickness over crest & facial slope of ridge should be? 
Select and explain. 
A. 1 mm, B. 2 mm, C. 3 mm, D. 4 mm
A: 1 mm
Answer: A: 1 mm 
Explanation: Record base thickness:
Crest & facial slope of ridge = 1 mm (Less thickness helps to provide additional space for teeth placement)
Hard palate & Lingual flange in mandibular denture base = 2 mm (Provide strength & rigidity)