Correct option is C
Passive sensors detect natural energy that is emitted or reflected by objects. The most common source of energy used by passive sensors is sunlight, as they rely on solar radiation to detect and measure reflected light or emitted radiation from the Earth's surface. Examples of passive sensors include cameras and radiometers that work without emitting their own signals or energy.
Signals from transmission towers are not relevant to passive sensors, as they are used in active sensing systems like radar.
Passive sensors do not generate their own energy, which is a characteristic of active sensors.
Flashlight, as an artificial source of energy, is also used in active sensing.
