Sound waves are longitudinal waves and the particles of the air move in direction of propagation sound. So if the wave will travel in west-east direction,the particles of the air also travels in west-east direction.

(i) False [Sound is produced from a vibrating object.]

(ii) True [The sound of a tabla normally has a lower pitch than the sound of a violin.]

(iii) True[A short flute will produce sound of lower pitch than a long flute.]

Longitudinal waves are made up of compressions and rarefactions. Compression happens when molecules are forced, or pressed, together. Rarefaction is just the opposite, it occurs when molecules are given extra space and allowed to expand. So, the longitudinal movement of air molecules produces pressure fluctuations which results in compression and rarefaction.

Frequency heard in the air will also be $600\space Hz.$ Whenever, the wave travels from one medium to another medium, its speed and wavelength changes but frequency remains same.

the point that there is a local change in temperature due to the compression and rarefaction half$-$ cycles of the waveform and that the these changes occur so quickly that no heat can enter or leave the cycle$,$

Sound waves are longitudinal waves and the particles of the air move in direction of propagation sound. So if the wave will travel in south-north direction,the particles of the air also travels in south-north direction.

A wave is a disturbance caused in a medium. In the case of sound, only the disturbances moves causing the surround air molecules to vibrate to and fro. The disturbance is transmitted in the form of compressions and rarefactions.

The speed of the sound, distance traveled and the time taken relationship if the sound is a reflected sound, that is echo, it is given as follows.
$Speed\; of \; sound=\dfrac { 2\times Distance\; traveled\; (m) }{ Time\; taken(s) } $.
In the question it is given that distance traveled by the sound from the source to the reflector is d and the time taken to hear the echo are $t _1$ and $t _2$ seconds.
The speed of the sound wave is calculated as follows.$v=\dfrac { 2d }{ t _1-t _2 } m/s$.

The echo is the sound reflection from a surface. Thus, total distance be covered by sound is $d=2\times 225=450 m$.

Time taken by the wave to travel from the sound to the reflecting surface $= t = \dfrac{30}{2} = 15 m$
Speed $= 342 m/s$ 
Distance of reflecting surface from the sound $= 342 \times 15 = 5130 m$

Given, Speed of sound, $v = 346 ms^{-1}$ Time taken for hearing the echo, $t = 4 s$
Distance travelled by the sound $ = v \times t = 346 m/s \times 4 s = 1384 m$
In 4 s sound has to travel twice the distance between the cliff and the person.
Hence, the distance between the cliff and the person $= 1384 m/2 = 692 m$

Minimum time for echo is $0.15$
So, distance travelled for echo is $=2\times 16.75=$ speed of sound $\times$ minimum time for echo
$\Rightarrow 2\times 16.75=\vartheta _{s}\times 0.1$

Let distance of hill from the position of the body = d
Echo is heard after 6 sec
$d = v \dfrac{t}{2}$
$= \dfrac{(340 \times 6)}{2}$
$= 1020 m$

Let $d$ be the distance of shack from the sonar . Therefore  distance covered by sound to come back to sonar after reflection from shack ,  $=d$ ,