In a Carnot’s engine, as the gas absorbs heat energy from the source, then the temperature of the source:
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In a Carnot engine, the temperature of the source remains constant during the heat absorption process, as the system is in thermal equilibrium with the source.
In a Carnot engine, the temperature of the source remains constant while the gas absorbs heat. The heat absorbed from the source is used for the expansion of the gas.
Thus, the correct answer is option (3).