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
Amalgam exhibits a Poisson’s ratio of 
Select and explain. 
A. 0.3, B. 0.5, C. 0.6, D. 1
A: 0.3
Answer: A: 0.3 
Explanation: Most rigid materials, such as enamel, dentin, amalgam, and dental composite, exhibit a Poisson’s ratio of about 0.3. Brittle substances such as hard gold alloys and dental amalgam show little  permanent reduction in cross section during a tensile test.
More ductile materials such as soft gold alloys, which are high in gold content, show a higher degree of reduction in cross-sectional area and higher Poisson’s ratios. 
Rubber has a Poisson’s ratio of nearly 0.5. 
Cork exhibits little lateral expansion under compression and has a Poisson’s ratio close to 0. 
This property has made cork a common material for sealing wine bottles.
Ref:Craig’s Restorative Dentistry ed 14th pg 36