As cells are using oxygen to produce energy they also produce carbon dioxide.
(they; also produce; carbon dioxide) (cells; are using; oxygen; to produce energy) Context(cells are using,List([3, 18))):(cells; are using oxygen to produce; energy they also produce carbon dioxide)
cells are using,List([3, 18))
they cells cells
also produce are using are using oxygen to produce
carbon dioxide
oxygen to produce energy
energy they also produce carbon dioxide