The chemical formula for sodium citrate is Nag Cs H5O7

Which statement is true?

A. Sodium citrate is a compound with a total of 21 atoms, each of a different element.

B. Sodium citrate is an element with a total of 21 atoms.

C. Sodium citrate is a compound with a total of 21 atoms.

D. Sodium citrate is a compound with a total of 4 atoms.​