Which of the following is a longitudinal wave?

What is the velocity of a wave in a monoatomic gas having a pressure of $1 \, kPa$ and a density of $2.6 \, kg/m^3$?

The velocity of sound in air is doubled when the temperature is raised from $0^{\circ} C$ to $\alpha^{\circ} C$. The value of $\alpha$ is . . . . . . .

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

Why are the speeds of longitudinal and transverse waves in a solid different? Explain.

On a windless day,sound emanates isotropically from a point source. Rays of the sound waves emanated from a point source placed close to the ground are shown in the figure. Consider horizontal wind towards the left blowing with constant velocity,which is uniform everywhere. In the following figures,rays of sound waves in the presence of the wind are shown. Which one is the most correct representation?