Endurance limit is not exactly a property of material.

Explanation:
Materials have various mechanical properties that describe their behavior under different types of loads and conditions. These properties help engineers and scientists understand how materials will perform in different applications. Some of the most important properties of materials include ultimate tensile strength, elastic modulus, yield stress, and endurance limit.

Ultimate Tensile Strength:
The ultimate tensile strength is the maximum stress a material can withstand before it breaks or fractures. It is an important property for materials that will experience tension or stretching forces.

Elastic Modulus:
The elastic modulus, also known as Young's modulus, is a measure of the stiffness or rigidity of a material. It describes how much a material will deform under an applied stress and how well it can return to its original shape when the stress is removed.

Yield Stress:
The yield stress is the stress at which a material begins to deform permanently or exhibit plastic behavior. It is an important property for materials that will experience plastic deformation, such as metals.

Endurance Limit:
The endurance limit is the maximum stress level below which a material can withstand an infinite number of cycles without failing. It is also known as the fatigue limit. This property is particularly important for materials that will undergo cyclic loading or fatigue, such as those used in rotating machinery or structural components subject to repeated loading.

However, not all materials have an endurance limit. Some materials, especially brittle materials like ceramics and certain types of polymers, do not exhibit a well-defined endurance limit. Instead, they fail catastrophically under cyclic loading, even at relatively low stress levels.

Therefore, the correct answer is option A, the endurance limit is not exactly a property of all materials.