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
Conventional dental amalgam alloy contains: 
Select and explain. 
A. Silver, tin, copper and zinc, B. Silver, mercury, copper and zinc, C. Silver, tin, palladium and zinc, D. Silver, copper, iridium and mercury
A: Silver, tin, copper and zinc
Answer: A: Silver, tin, copper and zinc 
Explanation: None