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. 

Example Input: Fuels burns in the combustion chamber. The burning fuel creates energy. The upward motion cause air to be released into the cylinder. The piston compresses the air. A spark ignites the fuel and air inside the cylinder. The pressure pushes the piston down. The exhaust valve opens. The piston pushes the air out of the cylinder. 
Example Output: fuel ,air ,spark ,pressure 

Example Input: Energy is created by burning either diesel or petrol in a combustion chamber. The energy is transferred from the pistons moving up and down at high speeds. This piston motion is converted to a rotary motion through the crankshaft and axle. The axle turns the wheels. The car moves forward. 
Example Output: diesel ,petrol ,energy ,pistons ,piston motion ,rotary motion ,car 

Example Input: There is a lot of rain. Water levels of a river or lake get higher. Water builds up on the ground. Water covers streets. Water goes into houses. The rain or other source of water stops. Water flows into streams. The rest of the water evaporates. 
Example Output:
rain ,water ,streams ,water levels