When pressure on a gaseous medium is changed at constant temperature,what will be the effect on the speed of sound wave in it?

The frequency of a rod is $200 Hz$. If the velocity of sound in air is $340 m/s$,the wavelength of the sound produced is:

Two sound sources produce waves at a certain temperature in air with wavelengths $50 \text{ cm}$ and $50.5 \text{ cm}$ respectively. The frequencies of the sources differ by $6 \text{ Hz}$. The velocity of sound in air at the same temperature is (in $\text{ m/s}$)

Which of the following is not a transverse wave?

What is the ratio of the velocity of sound in hydrogen $\left(\gamma=\frac{7}{5}\right)$ to that in helium $\left(\gamma=\frac{5}{3}\right)$ at the same temperature? (Molecular weight of hydrogen and helium is $2$ and $4$ respectively)

$A$ student plotted the following four graphs representing the variation of velocity of sound in a gas with the pressure $P$. Which one is correct?