 "process paragraph : : Water comes into contact with something made of iron. The water combines with carbon dioxide in the air to form carbonic acid. As the acid is formed, the iron starts to dissolve. Some of the water breaks down into hydrogen and oxygen. The free oxygen and dissolved iron bond together. They form iron oxide, which is rust. ", "event : The water combines with carbon dioxide in the air to form carbonic acid.", "entity : water" 
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