cellular digestion is when a room absorption from space and walking into oxygen dioxide, water, and matter & inanimate nothing require magnesium to waste matter ->  living things must convert oxygen into carbon dioxide to use energy  living things must convert oxygen into carbon dioxide to use energy & smother is when people pervert space into oxygen oxygen ->  living things must breathe to use energy  smother out is when people exhale oxygen oxygen from their blacktop into the land & people are a sink of oxygen oxygen by exhaling ->  animals are a source of carbon dioxide by breathing  animals are a source of carbon dioxide by breathing & a sink of something starling that something ->  animals produce carbon dioxide by breathing  living things must breathe to use energy & animals produce carbon dioxide by breathing -> animals produce carbon dioxide by using energy