chemical formula for a compound, chemistry homework help

How can one tell from a chemical formula whether a substance is an element or a compound?

A. The chemical formula for a compound contains two or more different elements while the chemical formula for an element only shows one type of atom.

B. The chemical formula for a compound always contains two elements while the chemical formula for an element is shorter.

C. The chemical formula for a compound is simpler than the chemical formula for an element.

D. The chemical formula for an element is made up of only one atom while the chemical formula for a compound will always have more than one atom.

E. The chemical formula for a compound contains two or more different types of atoms, indicating that it is a mixture of elements.