Enter a balanced chemical equation for the reaction of solid strontium with bromine gas. Express your answer as a chemical equation. Identify all of the phases in your answer.

a) Sr(s) + Br₂(g) → SrBr₂(s)
b) Sr(s) + Br₂(g) → SrBr(g)
c) Sr(s) + Br₂(g) → SrBr₄(s)
d) Sr(s) + Br(g) → SrBr₂(s)