Answer
A) Pt is an element, and $Pt(NH_3)_2Cl_2$ is a compound.
B) Copper is an element, and copper(II) oxide is a compound.
C) Silicon is an element, and sand is a compound.
Work Step by Step
A) Pt is an element, and $Pt(NH_3)_2Cl_2$ is a compound.
B) Copper is an element, and copper(II) oxide is a compound.
C) Silicon is an element, and sand is a compound.