Here's why:

* Light-dependent reactions (light reactions) of photosynthesis: These reactions directly use light energy to split water molecules. This process releases oxygen as a byproduct. So, oxygen is not a raw material in this case, but a product.

* Dark reactions (Calvin cycle) of photosynthesis: While these reactions don't directly require light, they do use carbon dioxide as a raw material. This carbon dioxide is ultimately incorporated into sugars. Oxygen is not a raw material for the Calvin cycle, but it is used in cellular respiration, which is linked to the Calvin cycle.

* Cellular respiration: This process breaks down glucose (sugar) to generate energy. It requires oxygen as a raw material to produce ATP (energy) and water as a byproduct.

Therefore, both light-dependent and dark reactions of photosynthesis, as well as cellular respiration, involve reactions that require oxygen as a raw material.