Which two qualities describe the structure of thermoplastics?

The choice identifying long linear chains and weak bonds accurately describes the structure of thermoplastics.

Thermoplastics are composed of long, linear polymer chains that can slide past one another when heated. This structure allows them to become pliable when subjected to heat, enabling them to be molded and reshaped multiple times without undergoing any significant chemical change. The weak intermolecular forces between these long chains facilitate their ability to soften under heat and harden upon cooling, which characterizes the thermoplastic behavior.

This contrasts with rigid and brittle materials, which do not exhibit the same malleability. Short chains and strong bonds would indicate a different type of material, typically leading to more rigid and less flexible properties, while solid and unchangeable refers to thermosetting plastics, which retain their shape after being set permanently.