Why can we not have a conversation on the surface of the Moon?

Sound travels in rocks in the form of

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?

If at the same temperature and pressure,the densities of two diatomic gases are respectively $d_1$ and $d_2$,then the ratio of the velocities of sound in these gases will be

$A$ car is moving with a speed of $72 \,km/h$ towards a hill. The car blows its horn at a distance of $1800 \,m$ from the hill. If the echo is heard after $10 \,s$,the speed of sound (in $m/s$) is:

Does an oscillating source always produce sound waves?