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:
The outer ear collects sound waves. The sound waves travel from the outer ear to the middle ear. The eardrum changes the sound waves into vibrations. The hammer, anvil, and stirrup bones vibrate. The sound moves to the inner ear. The sound enters the liquid-filled cochlea. The cochlea vibrates. Small hairs in the cochlea move. Nerve signals are created. The brain understands the nerve signals as sound. 
answer:
sound waves ,vibrations ,sound ,nerve signals 


question:
Energy builds up in the crust of the earth. The energy causes the fault lines give way. The earth's plates move. The energy radiates outward from the fault in all directions. The seismic waves shake the earth as they move through it. 
answer:
energy ,fault lines ,earth's plates ,seismic wave 


question:
One type of air pollution is the addition of carbon dioxide gas into the air. Some scientists believe that releasing too much carbon dioxide into the atmosphere is one of the causes of global warming. This upsets the balance of the carbon cycle. The ozone layer helps protect us from harmful rays from the sun. It is getting damaged from air pollution such as methane gas from livestock and CFCs from spray cans. Acid rain is created when gasses such as sulfur dioxide get high into the atmosphere. The wind can blow these gasses for miles and then they get washed out of the air when it rains. This rain is called acid rain and can damage forests and kill fish. 
answer:

ozone layer ,acid rain ,forests ,fish 


