Sum the Following Elementary Steps in a Mechanism to Determine $\rightarrow$

Sum the following elementary steps in a mechanism to determine the stoichiometry of the overall reaction.
Cl₂(g) $\rightarrow$ 2Cl(g)
Cl(g) + CO(g) $\rightarrow$ COCl(g)
COCl(g) + Cl(g) $\rightarrow$ COCl₂(g)

A) Cl₂(g) + 2 CO(g) + 2 Cl(g) $\rightarrow$ 2 COCl₂(g)
B) 2 Cl₂(g) + CO(g) $\rightarrow$ COCl₂(g) + 2 Cl(g)
C) 2 Cl(g) + CO(g) $\rightarrow$ COCl₂(g)
D) Cl₂(g) + CO(g) + Cl(g) $\rightarrow$ COCl₂(g) + COCl(g)
E) none of these