Which is a compound?

A. Nickel and oxygen reacting chemically

B. A spoon made of pure silver

C. A sandwich with bread, meat, and cheese

D. Long and short nails in a box

(A.) Nickel and oxygen reacting chemically could create a compound. (Most likely some sort of oxide)

The pure silver is only made up of one element, so it can't be a compound.

The sandwich and all it's components may contain chemical compounds, but is not a compound in itself.

While it is possible that the material the nails are made out of is a compound, we are not given this information. Simply stating that nails (no matter the size) are in a box, does not make it a compound.