if something releases something else then that something is the source of that something else & animal are a sink of space through siberian ->  plants release oxygen during photosynthesis  a plant absorbs carbon dioxide from the air to perform photosynthesis & to absorb something can mean to take something in -> a vegetable vegetation in oxygen oxygen to perform inside a plant takes in carbon dioxide to perform photosynthesis  plants release oxygen during photosynthesis & a vegetable vegetation in oxygen oxygen to perform inside -> plants take in carbon dioxide and release oxygen during photosynthesis