Narendra Dinkar Kharat

Activation of C-H means that you activate this functional group so that its activation energy is sufficient to undergo a chemical reaction, for example, when replacing a hydrogen atom with a chlorine atom.

This replacement will mean functionalization.

For example, you irradiate methane and chlorine molecules with ultraviolet light, you get methyl chloride. You have activated the methane molecules and obtained a new functional material.