The curvature of the earth
The ground wave propagation
The line of sight direction
transmit low frequency information over long distances efficiently
Produce side bands
Acquire wave shaping of the carrier wave
Combine two waves of different frequencies
The amplitude of the carrier wave varies in accordance with the amplitude of the modulating signal.
The amplitude of the carrier wave remains constant
The amplitude of the carrier varies in accordance with the frequency of the modulating signal
Modulating frequency lies in the audio range
Twice the signal frequency
Thrice the signal frequency
Four times the signal frequency
Equal to the signal frequency
Both the phase and the frequency of the carrier wave varies.
There is no change in the frequency and phase of the carrier wave
Only the phase of the carrier wave varies
Only the frequency of the carrier wave varies.
High frequency carrier waves
both audio signal and high frequency carrier waves
Low frequency carrier waves.
To avoid flicker in the picture
The fact that handling of higher frequencies is easier
that 50 Hz is the power line frequency in India
To avoid unwanted noises in the signals
Here's an interesting quiz for you.