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 pure form of gold used in dentistry is known as: 
Select and explain. 
A. Cohesive gold, B. Noncohesive gold, C. Class I casting gold, D. Class IV casting gold
A: Cohesive gold
Answer: A: Cohesive gold 
Explanation: Cohesive gold
For cold-welding, gold should have a clean surface free from impurities. Gold attracts gases, e.g., oxygen to its surface and any absorbed gas film prevents cohesion of individual increments of gold during their compaction. The manufacturer, therefore, supplies the gold essentially free of surface contaminants.This type of gold is known as cohesive gold foil.
Ref: Mannapallil basic dental materials 3 ed page no 114