Which Is Not Generally Considered to Be a Chemical Reaction

Which is not generally considered to be a chemical reaction of the alkaline earth metal calcium?

A) Ca(s) + Cl₂(g) → CaCl₂(s)
B) 2 Ca(s) + 2 H₂O(l) → 2 Ca(OH) ₂(aq) + H₂(g)
C) 6 Ca(s) + 2 N₂(g) → 2 Ca₃N₂(s)
D) Ca(s) + O₂(g) → CaO₂(s)