Q1: At room temperature, F.C.C. crystal structure is observed in

ANS:A - lead

Lead typically exhibits a face-centered cubic (FCC) crystal structure at room temperature. This crystal structure is characterized by atoms arranged in a cubic lattice with additional atoms located at the center of each face of the cube. In the case of lead, this arrangement allows its atoms to efficiently pack together, resulting in the FCC structure. This structure contributes to lead's relatively high malleability and ductility, making it useful for various applications such as construction, battery manufacturing, and radiation shielding. Additionally, lead's FCC crystal structure provides insight into its physical properties and behavior under different conditions.