Which of the following gases do plants and trees give out during photosynthesis?

The correct answer is C) Oxygen.

Plants and trees release oxygen during the process of photosynthesis. Photosynthesis is the process by which plants convert light energy from the sun into chemical energy in the form of glucose, which they use as food. During this process, carbon dioxide is taken in by the plant and oxygen is released into the atmosphere. This oxygen is essential for the survival of many organisms, including humans, who breathe in oxygen to support cellular respiration. Hydrogen and nitrogen are not typically released by plants during photosynthesis, while carbon dioxide is taken in and used as a reactant.