If the bond length of C-Cl bond in chloromethane is 178pm, what will be the probable bond length of C-Br bond in bromomethane?

139pm 156pm 178pm 193pm

193pm

The size of Cl atom is smaller than the size of Br atom as the latter appears lower than Cl in the halogen group. Hence, the carbon-halogen bond length of C-Br must be bigger than that of C-Cl, i.e., 178pm, therefore it must be 193pm.