The step not involved in the carbon cycle is (b) Transpiration.
Explanation: Transpiration is the process of water movement through a plant and its evaporation from leaves, which is primarily related to the water cycle, not the carbon cycle.
Why other options are correct:
Photosynthesis:
Plants absorb carbon dioxide from the atmosphere during photosynthesis to produce glucose, thus incorporating carbon into the food chain.
Respiration:
Both plants and animals release carbon dioxide into the atmosphere as a byproduct of cellular respiration.
Burning of fossil fuels:
Human activities like burning fossil fuels release large amounts of carbon dioxide into the atmosphere.