Remember that oxygen is used, and the by-product is carbon dioxide, which is used by plants in photosynthesis to produce oxygen again.
(the by-product; is; carbon dioxide, which is used by plants in photosynthesis to produce oxygen again) (carbon dioxide; is used; by plants in photosynthesis; to produce oxygen again) (carbon dioxide; to produce; oxygen; T:again)
the by-product carbon dioxide carbon dioxide
is is used to produce
carbon dioxide, which is used by plants in photosynthesis to produce oxygen again
by plants in photosynthesis to produce oxygen again
oxygen T:again