TASK 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. 
PROBLEM: Fuel is converted to energy when air and petrol mix. The car engine burns the mix of air and petrol. Hot gas from the burning pushes the pistons. The resulting energy powers the crankshaft. Crankshaft powers the gears. The gears make the wheels roll. 

SOLUTION: air ,petrol; fuel ,energy ,hot gas 

PROBLEM: Electricity enters the power supply unit. The power supply gives electricity to transistors. The power supply gives electricity to the CPU. The systems use electricity to complete tasks. The signals they complete are sent out as visual signals. The energy is used to complete computations. 

SOLUTION: electricity; energy ,visual signals ,computations 

PROBLEM: Pressure happens underground. Tectonic plates underground pull and stretch. Small cracks are formed in the earth's crust. The tectonic plates push hard against each other. Some parts of the earth's crust move up high above the ground. 

SOLUTION:
pressure ,tectonic plates ,cracks ,earth's crust