If the height of the transmitting tower is increased by $30 \%$,then the area covered by it increases by (in $\%$)

Television signals on earth cannot be received at distances greater than $100\, km$ from the transmission station. The reason behind this is that

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.

Define the following terms:
$(a)$ Ground waves
$(b)$ Trade winds

What is the frequency range of signals that can be transmitted using a $Twisted\, pair\, wire$?

For an $FM$ carrier with a carrier frequency of $200 \text{ kHz}$ and a modulating frequency of $10 \text{ kHz}$,the modulation index is...