Creep strength is the structure sensitive property among the given options.

Explanation:
Structure sensitive properties are those properties of a material that depend on the arrangement and distribution of its atoms or molecules within the material's structure. These properties are influenced by the microstructure of the material, including factors such as grain boundaries, dislocations, and defects.

Here is a detailed explanation of each option and why creep strength is the structure sensitive property:

a) Elastic contacts: Elastic contacts refer to the ability of two surfaces to maintain contact without permanent deformation when subjected to an external load. While the elasticity of a material is affected by its structure, the concept of elastic contacts does not directly relate to the microstructure of the material. Therefore, it is not a structure sensitive property.

b) Density: Density is a measure of how much mass is contained in a given volume of a material. Density is primarily influenced by the atomic or molecular mass of the material and does not depend on the arrangement of atoms or molecules within its structure. Hence, density is not a structure sensitive property.

c) Creep strength: Creep strength refers to the ability of a material to resist deformation under prolonged exposure to high temperatures and constant stress or load. Creep is a time-dependent phenomenon that occurs due to the movement of atoms or molecules within the material's structure. It is influenced by the microstructure of the material, including factors such as grain boundaries, dislocations, and defects. Therefore, creep strength is a structure sensitive property.

d) Specific heat: Specific heat is the amount of heat energy required to raise the temperature of a unit mass of a material by a certain amount. It is primarily influenced by the atomic or molecular structure of the material and the types of interatomic or intermolecular forces present. However, specific heat does not directly depend on the arrangement of atoms or molecules within the material's structure. Hence, specific heat is not a structure sensitive property.

In summary, among the given options, creep strength is the structure sensitive property as it is influenced by the microstructure of the material.