Q1: Material having negative co-efficient of linear expansion is

ANS:C - rubber

A material with a negative coefficient of linear expansion means that it contracts when heated and expands when cooled. Among the options provided, rubber is the material with a negative coefficient of linear expansion. Rubber exhibits a unique behavior where its length decreases when heated and increases when cooled. This phenomenon is known as negative thermal expansion or auxetic behavior. It is due to the complex molecular structure of rubber, which includes the arrangement of polymer chains and intermolecular forces. So, the correct option is: rubber.