What is the primary characteristic of brittle rock behavior?

The primary characteristic of brittle rock behavior is the ability to break easily under stress. When subjected to stress, brittle rocks tend to fracture rather than deform. This behavior is typical in materials that cannot accommodate significant deformation without failing, such as granite and certain forms of sedimentary rock. The fractures that occur often result in distinct, sharp edges, indicative of the abrupt nature of the failure.

In contrast, the other characteristics outlined in the options describe different behavioral responses to stress or environmental conditions. For example, the ability to bend without breaking relates to ductile materials, which can deform smoothly under stress. Similarly, the ability to flow under pressure pertains to materials that behave plastically rather than fracturing. Lastly, the ability to absorb heat without melting refers to thermal properties that are not directly related to mechanical stress responses in rocks. Thus, the behavior of brittle rocks distinctly highlights their propensity to fail suddenly when subjected to stress, making the ability to break easily the defining characteristic.