Which of the following has the highest C-X bond length?
Bond length increases with the size of the halogen. Among F, Cl, Br, and I, iodine is the largest, so CH₃-I has the longest C-X bond.
Ref: NCERT Class 12 Chemistry > Chapter 6: Haloalkanes and Haloarenes > Topic: Nature of C-X Bond and Methods of Preparation