Which property characterizes elastomers in materials science?

Elastomers are a class of materials known for their unique ability to stretch and then return to their original shape when the load is removed. This characteristic is fundamental to their definition and makes them particularly useful in applications requiring flexibility and resilience. When an elastomer is stretched, its molecular structure is pulled apart, allowing the material to deform. Upon the release of the stress, the polymer chains return to their original configuration due to their inherent elasticity. This property allows elastomers to absorb energy and withstand repeated loading and unloading without permanent deformation, making them ideal for various applications, such as seals, gaskets, and flexible components in a myriad of mechanical systems.

The other options describe properties that do not accurately characterize elastomers. For instance, being rigid and non-flexible contradicts the essential characteristic of elastomers, which is their flexibility. Maintaining shape under stress is not a defining trait of elastomers; they can deform significantly under stress but recover afterward. Lastly, having high thermal conductivity is not a typical feature of elastomers, which usually have low thermal conductivity due to their polymer nature. Therefore, the answer highlights the core property of elastomers that distinguishes them from other materials.