From where does the o2 come that is produced as a by-product of photosynthesis?

Landfills are waste disposal sites. they are often man-made depressions in the ground covered with a lining designed to prevent any leakage of waste materials. however, landfills can leak through the base resulting in negative impacts on the surrounding environments. what negative impact to the environment is caused by organic and inorganic constituents that are dissolved by rainfall in the landfills?

Can someone me with this and tell me what’s fracking and what does it have to do with carbon, carbon dioxide, or fossil fuels?

Why did adult crab numbers decline in he ecosystem, even though sea stars were still available?