Which of the following is not a transverse wave?

$A$ sound is produced by plucking a string in a musical instrument,then

The speed of sound in mercury at a certain temperature is $1450 \, m/s$. Given the density of mercury as $13.6 \times 10^3 \, kg/m^3$,the bulk modulus for mercury is:

$A$ plane wave of sound traveling in air is incident upon a plane surface of a liquid. The angle of incidence is $60^{\circ}$. The speed of sound in air is $300 \ m/s$ and in the liquid it is $600 \ m/s$. Assume Snell's law to be valid for sound waves.

If the velocity of sound in a gas is $360\, m/s$ and the distance between a compression and the nearest rarefaction is $1\, m$,then the frequency of sound is ..... $Hz$.

At what temperature is the velocity of sound double that of its velocity at $0^{\circ}C$?