The ratio of the noise bandwidth in hertz to the theoretical bandwidth of a resistive network
The ratio in dB of the noise generated in the receiver to atmospheric noise
The ratio in dB of the noise generated by the receiver to the theoretical minimum noise✓Correct answer
Explanation
Noise figure states in dB how much noise the receiver adds beyond the unavoidable thermal minimum, so an ideal noiseless receiver has a noise figure of 0 dB. It is a property of the receiver itself, not a comparison with atmospheric noise or a ratio of bandwidths.