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
Modulus of elasticity means: 
Select and explain. 
A. Rigidity or stiffness of the material, B. Ability to be stretched with permanent deformation, C. Ductility of a material, D. Malleability of the metal
A: Rigidity or stiffness of the material
Answer: A: Rigidity or stiffness of the material 
Explanation: ELASTIC MODULUS (YOUNG’S MODULUS OR MODULUS OF ELASTICITY)
The word stiffness should come to mind upon reading one of these three terms in the dental literature. Elastic modulus describes the relative stiffness or rigidity of a material, which is measured by the slope of the elastic region of the stress-strain graph.
Reference: PHILLIPS’ SCIENCE OF DENTAL MATERIALS, 12th ed page no 53