Which of the following statements are true?
a. two materials may have similar elastic constants but have vastly different breaking stresses.
b. an object can experience both tensile and compressive stresses at the same time.
c. strain is characterized by the strength of the forces causing deformation, on a "force per unit area" basis.
d. the elastic modulus can be determined from the ratio of the strain to the stress.
e. stress is characterized by the strength of the forces causing deformation, on a "force per unit area" basis.