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.

[EX Q]: Two large veins bring blood to the heart. The blood enters the right atrium. The blood flows through the tricuspid valve. The blood travels into the right ventricle. The blood goes through the pulmonary arteries to the lungs. Blood picks up oxygen in the lungs. Oxygenated blood enters the left atrium. Blood goes to the left ventricle. Blood leaves the heart via the aorta to the rest of the body. The deoxygenated blood returns to the heart.
[EX A]: oxygenated blood ,deoxygenated blood ,oxygen

[EX Q]: People breathe and expel carbon dioxide. Engines produce carbon dioxide. Living things produce waste. Waste decomposes. Decomposition produces methane. Water evaporates. Water vapor joins the atmosphere. Carbon dioxide, water vapor and methane are greenhouse gases.
[EX A]: carbon dioxide ,methane ,water ,water vapor ,greenhouse gases

[EX Q]: Get the ice tray. Remove any ice cubes currently in the tray. Fill the tray with cold water. Ensure the tray is evenly filled to an appropriate level. Open the freezer. Place the tray in the freezer. Close the freezer door. Wait.
[EX A]:
ice tray ; tray ,ice cubes ,cold water