I think it is C. bcoz, it forms a more stabler intermediate, which undergoes mesomeric resonance within its ring, and hence is more stable.

In (c),

    (1)      (2)

 

if u rewrite ring 2 with the double bond from ring 1 in it, then, u'll find that it'll have 3 resonating structures, which adds to its stability. Hence more is the stability, faster is the formation of intermediate(as it has to cross a smaller energy barrier), and hence faster is the reaction.

 

Hope this helps