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: Magma rises through cracks in the Earth's crust. The pressure causes plates to move. Magma explodes to the surface. The lava from the eruption cools to form new crust. After several eruptions, the rock builds up and a volcano forms. 
Example Output: volcano ,magma ,pressure ,lava ,crust ,rocks 

Example Input: Choose what you want to write your letter on. Think of what you want to say. Write some nice things!. Place the letter into an envelope. Put a stamp on the top right corner of the face of the envelope. Write the address of the recipient on the envelope. Put the envelope in your mailbox. Raise the flag on your mailbox, indicating to the mailman that you have outgoing mail. 
Example Output: envelope ,flag on your mailbox ,letter ,nice things ,stamp 

Example Input: Electricity enters the computer. Some electricity becomes light. Some light becomes heat when it hits something. Some electricity becomes motion in a hard drive, dvd drive or fan. Motion energy also becomes heat. 
Example Output:
electricity ,light ,heat ,motion ,motion energy