I think your teacher probably wants this comic to come from you but here are some pointers:
Carbon comes from
- organisms decomposing after they die
- within CO2 that all animals breathe out
- human activities that burn fossil fuels like factories, driving cars, flying planes
Carbon is used by
- plants to make sugar (from CO2 —> glucose)
- animals as a nutrient to build macromolecules for their bodies (amino acids, nucleotides, carbohydrates, fats/lipids)
Draw the different sources contributing to the build up of carbon in the air, then illustrate arrows showing how the CO2 is brought back for use by plants or how carbon is used directly by organisms consuming dead material. Then demonstrate these events again releasing carbon, repeating the cycle.