The answer is B.
We can rule out A because metallic bonds only happen between metals, and chlorine is a halogen (not a metal).
We can rule out C because polar covalent bonds form between atoms with high electronegativity differences. Since the bond is between two atoms of the same type, they would both have the same EN value and therefore their EN difference would be zero.
We can also rule out D because ionic bonds occur between a metal and a nonmetal.
