Which of the following best describes the physical conditions that determine if a crack will propagate as described by the Griffith criterion? A crack will propagate if the strain energy released is smaller than the free surface energy created by the crack opening. A crack will not propagate unless the stress applied is greater than the yield strength of the material. A crack will propagate if the strain energy released is larger than the free surface energy created by the crack opening A crack will propagate if the strain is larger than the necking strain.