What is the modulation index of an over-modulated wave?

$A$ $TV$ transmitting antenna is $128 \ m$ tall. If the receiving antenna is at the ground level,the maximum distance between them for satisfactory communication in line-of-sight mode is (radius of the earth $R_e = 6.4 \times 10^6 \ m$):

If a $TV$ transmission is broadcast from a $TV$ transmitter tower of height $h$,then the maximum distance of this transmission is proportional to the height $h$ of the tower as.........

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.

The bandwidth of an optical fiber is approximately ........

$A$ transmitting antenna covers a range of $12.8 \ km$. Find the height of the antenna in $m$. (Radius of the Earth $= 6400 \ km$)