A body is 11.34 km below sea level. To confirm this depth, a research team sends down a sonar signal. How long will it take to hear the echo from the body? ( Consider the speed of sound in the sea as 1620 m/s)

If we shout or clap close to a suitable reflecting object, such as a tall building or a mountain, we will hear the same sound again a short time later. This sound we hear is known as an echo.

Echoes are caused by the phenomenon of sound wave reflection.

Given,
Depth $=11.34 \mathrm{km}=11340 \mathrm{m}$
Speed of sound in water $=1620 \mathrm{m}/\mathrm{s}$
Total distance covered by the Sound wave to return $=2\times$ depth 
$\Rightarrow 2\times 11340 \mathrm{m}=22680 \mathrm{m}$

We know,  $\mathrm{Speed}=\frac{\mathrm{Distance}}{\mathrm{Time}}$
$\Rightarrow$ Time $=\frac{22680}{1620}=14 s$

Therefore, 14 s is the correct response.