The waves used for line-of-sight $(LOS)$ communication are

$A$ transmitting antenna can cover an area of $6.4\pi \times 10^9 \ m^2$ when used for broadcasting. If the signal is transmitted to another antenna,which is at a distance of $100 \ km$ from this antenna,what should be the minimum height of the receiving antenna for satisfactory communication in line-of-sight mode (in $m$)? (Assume the radius of the Earth $R = 6400 \ km$)

Given below are two statements:
Statement-$I$: $A$ speech signal of $2 \, kHz$ is used to modulate a carrier signal of $1 \, MHz$. The bandwidth requirement for the signal is $4 \, kHz$.
Statement-$II$: The sideband frequencies are $1002 \, kHz$ and $998 \, kHz$.
In the light of the above statements,choose the correct answer from the options given below:

$A$ receiving station on the ground is receiving a signal of frequency $5 \ MHz$ from a transmitter. Then the signal can come via

An antenna of length $3 \ m$ will effectively radiate which frequency?

$A$ $TV$ transmission antenna is $40 \ m$ tall. How much service area can it cover if the receiving antenna is at the ground level? (Radius of the Earth $= 6400 \ km$)