The reduction of alkyl halides will depend on the bond strength of alkyl halide. Weaker the bond between them more easily will be their reduction.

Now, the bond strength depends on the size of halogen attached to the alkyl. Bigger the size of halogen, less will be the bond strength and thus the reduction will be easier. We know that I has the biggest size followed by Br and then Cl.

Therefore, the order of reduction will be (ii) R–Cl < R–Br < R–I.