The bandwidth of a coaxial cable is approximately ........ .

$A$ carrier signal of frequency $v_1$ and peak voltage of $V_1$ is modulated by a message signal of frequency $v_2$ and peak voltage of $V_2$. Let $m$ be the modulation index and $v_{+}, v_{-}$ be side bands produced. The correct statement is

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.

The process of increasing the strength of a signal using an electronic circuit is called

When the modulating frequency is doubled, the modulation index is halved and the modulating voltage remains constant, the modulation system is

For efficient transmission of sound waves of wavelength $\lambda$,the minimum length of the antenna should be.....