Which of the following statements is true about elastic limit?

The correct statement about the elastic limit is that it is the point where permanent deformation begins. The elastic limit defines the maximum amount of stress that a material can withstand while still returning to its original shape once the external forces are removed. When stress is applied to a material, it behaves elastically up to this limit; beyond this point, the material will undergo plastic deformation, meaning that it will not return to its original form even when the load is removed. Understanding the elastic limit is crucial in engineering and material science, as it helps in selecting materials for various applications, ensuring they can endure the required loads without sustaining permanent damage.

The other statements do not accurately represent the concept of elastic limit, as it is indeed relevant in the study of elasticity; it does not define how long a material can be stretched since it pertains to the extent of stress before deformation occurs; and it is not associated with the maximum stress the material can endure, but rather the threshold before permanent changes occur.