instruction:
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. 
question:
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. 
answer:
eggs ,bird ,flight feathers 


question:
A plant of animal dies in a watery environment. Is buried in mud and silt. Soft tissues quickly decompose leaving behind hard bones or shells. Over time sediment builds over the top and hardens into rock. As the bone decays mineral seeps in replacing it. Fossils are formed. 
answer:
plant; animal ,soft tissues ,bones ,mineral ,fossils 


question:
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. 
answer:

Solution caves ,carbon dioxide ,weak carbonic acid solution ,calcite ,solution cavities 


