Correct Answer - B
The atmospheric E region or E layer is above the D-region and below the F-region. It exists at altitude between 100 to 125 km above the earth surface E-layer assists in long distance radio communication.
In this layer, gases like oxygen and nitrogen are ionized due to photo-ionization by energy released from the sun during day time which facilitates in radio communication so, this layer does not work during in the night time.
