The correct answer is option 3, "Oxidation of carbohydrate," which is not a function of chlorophyll.

Option 1, "Splitting of water," is a function of chlorophyll. During the process of photosynthesis, chlorophyll captures light energy and uses it to split water molecules into oxygen and hydrogen ions.

Option 2, "Absorption of photons," is another function of chlorophyll. Chlorophyll molecules in plants absorb photons (light energy) from the sun, which is essential for photosynthesis.

Option 4, "Conversion of light energy into chemical energy," is also a function of chlorophyll. Through a series of biochemical reactions, chlorophyll converts light energy into chemical energy in the form of glucose or other carbohydrates.

Therefore, the correct answer is option 3, as chlorophyll does not play a role in the oxidation of carbohydrates.