Which of the following actions does not release carbon dioxide?
Photosynthesis
Photosynthesis is a process by which plants absorb carbon dioxide from the air and water from the roots to prepare food using sunlight with the help of chlorophyll. All other options release carbon dioxide in the air.
Decomposition is the process in which micro-organisms break organic material such as dead plants and animals into simpler substances. The break down of organic material through the help of micro-organisms releases carbon dioxide.
Respiration is the process by which living things take in oxygen in order to produce energy within their body and they release carbon dioxide out after the energy is generated and used.
Combustion is the process by which we burn something. The burning of carbon or carbon compounds leads to the production of carbon dioxide gas.
So photosynthesis is the only process among the given option that does not produce carbon dioxide instead uses it to produce food.