Question: how do trees make oxygen

Joe Sweeney answered on 10 Mar 2014:

One word: photosynthesis. This is the process by which plants and trees absorb carbon dioxide (CO2) from the air and water from the environment, and turn them into a foodstuff: glucose. The chemical reactions which convert CO2 (which has a very simple structure) into glucose (a complex structure) produce oxygen as a by-product. The oxygen (O2) is not needed and is given off by the plants and trees into the atmosphere