Through which mode of propagation can radio waves be sent from one place to another?

$A$ $TV$ transmission tower antenna is at a height of $20\, m$. Suppose that the receiving antenna is at:
$(i)$ ground level
$(ii)$ a height of $5\, m$.
The increase in antenna range in case $(ii)$ relative to case $(i)$ is $n\%$.
The value of $n$,to the nearest integer,is .....$\%$

This question has Statement-$1$ and Statement-$2$. Of the four choices given after the statements, choose the one that best describes the two statements.
Statement-$1$: Sky wave signals are used for long-distance radio communication. These signals are, in general, less stable than ground wave signals.
Statement-$2$: The state of the ionosphere varies from hour to hour, day to day, and season to season.

$A$ message signal of frequency $3\,kHz$ is used to modulate a carrier signal of frequency $1.5\,MHz$. The bandwidth of the amplitude modulated wave is

Modulation is a process of superposing

If the height of transmitting and receiving antennas are $80\,m$ each,the maximum line of sight distance will be $..............\,km$. Given: Earth's radius $= 6.4 \times 10^6\,m$.