Which of the following has a △Hf of zero?

Question

_______ has a ΔH_f of zero.

A. Br^-

B. Na⁺

C. H₂O

D. CO₂

E. O₂

For this I got E. O₂

Would this happen to be correct?

Answer 1

This would happen to be correct. It is the only choice for which the option is present in its standard form.