For the compounds 

${\mathrm{CH}}_3\mathrm{Cl},{\mathrm{CH}}_3\mathrm{Br},{\mathrm{CH}}_3\mathrm{I}\text{ and }{\mathrm{CH}}_3\mathrm{F}\text{, }$ the correct order of increasing C- halogen bond length is:

As the size of halogen atom increases, the bond length also increases in the same order i.e. 

$\mathrm{C}-\mathrm{F}<\mathrm{C}-\mathrm{Cl}<\mathrm{C}-\mathrm{Br}<\mathrm{C}-\mathrm{I}$