Which of the following best describes an elastic object beyond its limit of proportionality?

The correct choice highlights how an elastic object behaves when it is stretched beyond its limit of proportionality. When an object is deformed within its elastic limit, it can return to its original shape once the force is removed. However, once this limit is exceeded, the material may undergo permanent deformation, meaning it will not return to its original shape even after the applied force is taken away.

Beyond the limit of proportionality, the relationship between the force applied and the deformation is no longer linear, and the material can remain stretched, bent, or misshapen in a way that is not reversible. This characteristic ensures that the object has undergone a structural change at the molecular or atomic level, leading to a new equilibrium position.

In contrast, the other options do not accurately describe the behavior of elastic objects past their limit of proportionality. An object will not always return to its original shape after surpassing this limit, and stating that it behaves as a rigid body misrepresents its capacity to still experience changes. Additionally, while materials may degrade in performance over prolonged use, the statement about reduced elasticity over time does not specifically address the immediate effects of breaching the limit of proportionality.