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: Solution caves are formed in limestone and similar rocks by the action of water. After a rain, water seeps into cracks and pores of soil and rock. The water percolates beneath the land surface. Some of the water reaches a zone where all the cracks and pores in the rock are already filled with water. Rainwater absorbs some carbon dioxide as it passes through the atmosphere and even more as it drains through soil and decaying vegetation. The water combines chemically with the carbon dioxide. A weak carbonic acid solution is formed. This acid slowly dissolves calcite, forms solution cavities, and excavates passageways. 
Example Output: Solution caves ,carbon dioxide ,weak carbonic acid solution ,calcite ,solution cavities 

Example Input: Water gets caught in winds that are moving upward. The water freezes. The water starts to fall. The winds are strong enough from keeping it from falling back to earth. This pattern of rising and falling continues. The hail becomes too large to be pushed up by the wind. The hail finally falls to the ground. 
Example Output: water ,hail 

Example Input: Warm air from the surface rises into the higher cold air. The water vapor in the air is condensed. The condensed water and dust forms a cloud. Wind in the cloud bounces the water droplets around. The bouncing droplets join together. The bigger droplets get heavy. The heavy droplets fall. As they fall, they join with more moisture in the air. The droplets get larger. Rain falls. 
Example Output:
warm air ,water vapor ,condensed water ,dust ,cloud ,water droplets ; droplets ,moisture ,rain