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: An owl leaves his nest. The owl flys out into the night. The owl looks down at the ground. The owls keen eyesight allows him to see in the dark. The owls sensitive hearing allows him to locate hidden prey. The owl swoops down. The owl catches a mouse in his talons. 
Example Output: owl ,mouse 

Example Input: A male and female bird mate. The female lays eggs. The eggs are incubated by the parents, by sitting on them, for weeks. The bird hatches from an egg. The parents feed them as the continue to grow. Develop flight feathers. The parents teach them to fly. After learning to fly they leave the nest to live on their own. The next year they breed beginning the cycle again. 
Example Output: eggs ,bird ,flight feathers 

Example Input: Coal is burned in a boiler. Steam is produced under pressure. Flows into a turbine. The turbine spins. Creates electricity. 
Example Output:
coal ,steam ,turbine ,electricity