Among the following which one has weakest carbon-halogen bond ?

benzyl bromide dissociates to benzylic cation, bromobenzene dissociates to phenyl cation, vinyl bromide dissociates to vinylic cation and benzyl chloride dissociates to benzylic cation. Among the cations given above benzylic cation is the most stable due to its extended resonance stability.

Now C−Br bond is weaker than the C−Cl bond due to their size mismatching (Bromine is comparatively much larger than chlorine)