Definition: 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. 
Input: Plants start growing on or near the rocks. The roots of the growing plants start to break up the rock. The plant acids dissolve the rock. The rock is broken down into smaller pieces. Erosion begins. 
Output:
plants ,rocks ; rock ,roots ,smaller pieces 