Which of the following is not a transverse wave?

The speed of sound in oxygen $(O_2)$ at a certain temperature is $460 \, m/s$. The speed of sound in helium $(He)$ at the same temperature will be ............. $m/s$ (assume both gases to be ideal).

When a tuning fork vibrates,the waves produced in the fork are

The figure represents the instantaneous picture of a longitudinal harmonic wave travelling along the negative $x$-axis. Identify the correct statement$(s)$ related to the movement of the points shown in the figure. The points of maximum rarefaction are

Use the formula $v=\sqrt{\frac{\gamma P}{\rho}}$ to explain why the speed of sound in air:
$(a)$ is independent of pressure,
$(b)$ increases with temperature,
$(c)$ increases with humidity.

$A$ source of sound $S$ having frequency $f$. Wind is blowing from source to observer $O$ with velocity $u$. If the speed of sound with respect to air is $C$,the wavelength of sound detected by $O$ is: