Francine is developing a model of the carbon cycle, which involves the movement of carbon among various Earth systems. She begins by drawing the diagram shown below. Her friend Byron evaluates the model, and suggests that she thicken the arrow leading from fossil fuels to the atmosphere. His reasoning is that fossil fuels are being burned at a much faster rate than natural processes are restoring them.

Label the model to show where it represents photosynthesis, cellular respiration, and the burning of carbon-containing materials.