In this task, you are given a paragraph, and your job is to generate comma-separated entities present in the given paragraph. Generate entities from a given passage in such a way that (i) they are present in the paragraph, (ii) they are non-duplicate, (iii) they underwent a state change during the process. Avoid creating entities that (i) aren't present in the process paragraph and (ii) aren't significant. 
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Question: A fuel is heated in an oven. Above the oven is a tank of water that is sealed. The tank of water begins to boil above the oven. A the water boils steam is created. The steam is denser than air so it needs a place to go. The steam is forced out of the tank and into a piston. The piston moves up. The valve of the piston closes. The valve on the next piston opens. The steam fills the next piston, driving it up, and the other one down. 

Answer: fuel ,water ,steam 


Question: The human body takes a breath inward. Air is transported to the lungs. Air reaches the alveoli, the smallest air sacs in the lungs. In the alveoli, air passes into the blood within small capillaries. The gaseous oxygen in the air dissolves into the capillary blood. The dissolved oxygen is picked-up by red blood cells. The red blood cells bind the oxygen via a protein called heme. Red blood cells circulate throughout the body and reach the various tissues. Within small capillaries, the heme release the oxygen. The oxygen can then reach the cells within the tissue. 

Answer: air ,oxygen ,red blood cells 


Question: The liver takes in blood from the rest of the body. The liver uses enzymes to clean the blood. The cleaned blood is expelled. The liver creates bile from the items filtered. The liver takes energy and stores it as glycogen. The bile is sent to the intestines. 

Answer:
blood ,cleaned blood ,items filtered ,bile ,energy ,glycogen