Considering a group of positive charges, which of the following statements is correct ?

Given below are two statements :

Statement I : For transmitting a signal, size of antenna ( $l$ ) should be comparable to wavelength of signal (at least $l=\frac{\lambda}{4}$ in dimension)

Statement II: In amplitude modulation, amplitude of carrier wave remains constant (unchanged).

In the light of the above statements, choose the most appropriate answer from the options given below

A body of mass $10 \mathrm{~kg}$ is moving with an initial speed of $20 \mathrm{~m} / \mathrm{s}$. The body stops after $5 \mathrm{~s}$ due to friction between body and the floor. The value of the coefficient of friction is:

(Take acceleration due to gravity $g=10 \mathrm{~ms}^{-2}$ )

A hypothetical gas expands adiabatically such that its volume changes from 08 litres to 27 litres. If the ratio of final pressure of the gas to initial pressure of the gas is $\frac{16}{81}$. Then the ratio of $\frac{\mathrm{Cp}}{\mathrm{Cv}}$ will be.