The correct answer is option is infrared light.
The part of electromagnetic radiation that is used to make images based on the temperature of the objects is done by the infrared light.
All the objects emits some energy(heat ) in the form of temperature. The more hotter the object more radiation it emits.
The heat sensor (thermal camera) is capable of detecting tiny differences in the temperature of the object.
As the different objects have different temperature, image appear as distinct thermal image.