Question

which pair correctly matches a process with its immediate effect on co2?
cellular respiration releases co2
combustion - reduces co2
decomposition - removes co2 from air
photosynthesis - releases co2

Explanation:

Cellular respiration is a process where cells break down glucose and oxygen to produce energy, carbon dioxide ($CO_2$), and water. So, cellular respiration releases $CO_2$. Combustion (burning of fuels like fossil fuels) actually releases $CO_2$, not reduces it. Decomposition of organic matter by decomposers (like bacteria and fungi) releases $CO_2$ (when organic - carbon is oxidized), it does not remove $CO_2$ from the air. Photosynthesis is a process where plants use $CO_2$, water, and sunlight to produce glucose and oxygen. So, photosynthesis removes $CO_2$ from the air, not releases it.

Answer:

Cellular respiration - releases $CO_2$