For the compounds CH 3 Cl, CH 3 Br, CH 3 I and CH 3 F, the correct...

C-halogen bond length totally depends on the electronegativity difference between Carbon and halogen. The more the difference and the less is the bond length. The electronegativity order of halogens is $I < Br < Cl < F$. Hence, the correct order of increasing C-halogen bond length is $CH3F < CH3Cl < CH3Br < CH3I .$

Or we can say that as the size of halogen increases C-halogen bond length also increases.