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: Air is brought in through the mouth. Passes through the lungs. And into the bronchial tissue. The carbon dioxide is removed. The lungs bring the oxygen to the rest of the body. 
Example Output: air ,carbon dioxide ,oxygen 

Example Input: A frog lays eggs in the water. Tadpoles develop inside of the eggs. The eggs hatch. The tadpoles eat and grow. The tadpoles grow legs and form into frogs. The frogs leave the water. 
Example Output: frogs ,tadpoles ,eggs ,legs 

Example Input: Chemical reactions break down the bonds holding the rocks together. The rocks fall apart. They form smaller and smaller pieces. Oxidation takes place when oxygen combines with other elements in rocks. They form new types of rocks. The new substance is softer. Carbonation takes place when carbon dioxide reactions with certain types of rocks. A solution is formed that can easily be carried away by water. 
Example Output:
rocks ; smaller pieces ,oxygen ,new types of rocks ; new substance ; certain types of rocks