In the process of modulation,the audio waves are called ...........

Given below are two statements
Statement $I:$ For transmitting a signal,the size of the antenna $(l)$ should be comparable to the wavelength of the signal (at least $l = \frac{\lambda}{4}$ in dimension).
Statement $II:$ In amplitude modulation,the amplitude of the carrier wave remains constant (unchanged).
In the light of the above statements,choose the most appropriate answer from the options given below.

Space wave propagation is possible for which frequency range?

The characteristic impedance of a coaxial cable is of the order of .......... $\Omega$.

The mathematical form of an $AM$ wave is given by $e = 50 (1 + 0.5 \sin (2\pi \times 5 \times 10^{3}) t) \sin (31.4 \times 10^{6}) t \, V$. To generate this $AM$ wave,the amplitudes of the carrier wave and the modulating wave must be,respectively,....... and ....... .

Which of the following is the disadvantage of $FM$ over $AM$?