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: Stars burn mass. The star burns until it runs out of fuel. The star can no longer support its weight. The layers of hydrogen press down on the core. The core gets smaller and smaller under the pressure. The pressure causes gravity to get stronger. The gravity becomes so powerful that nothing can escape it. Anything that gets close to it, is drawn into it by its gravity. Light is drawn into it. Light can not escape. 
Example Output: Mass ,Fuel ,Gravity 

Example Input: The gravity of the sun pulls its mass inward. There is a lot of pressure on the Sun. The pressure forces atoms of hydrogen to fuse together in nuclear reactions. The energy from the reactions gives off different kinds of light. The light travels to the Earth. 
Example Output: atoms of hydrogen ,sunlight; light 

Example Input: Solar panels actually comprise many, smaller units called photovoltaic cells. Photovoltaic simply means they convert sunlight into electricity.). Many cells linked together make up a solar panel. Each photovoltaic cell is basically a sandwich made up of two slices of semi-conducting material, usually silicon : . Manufacturers "dope" silicon with other materials, giving each slice of the sandwich a positive or negative electrical charge. This adds extra electrons, with a negative charge, to that layer. Meanwhile, the bottom layer gets a dose of boron, which results in fewer electrons, or a positive charge. This all adds up to an electric field at the junction between the silicon layers. When a photon of sunlight knocks an electron free, the electric field will push that electron out of the silicon junction. A couple of other components of the cell turn these electrons into usable power. 
Example Output:
sunlight ,electrictiy ,solar panel ,electric field 

