The correct answer is D.
Echo refers to the sound that is heard when a sound wave is reflected back from a surface. An echo sound is made when a sound wave traveled through the air, hit a hard surface and get reflected back. Generally, hard surfaces reflect sound wave while soft surfaces absorb sound waves. Reflected sound waves are used in application of some devices that are used in range and direction finding.
Elements of iodine are fluorine, chlorine, bromine, and astatine.
Answer:
<h2>6 m/s</h2>
Explanation:
The speed of the man can be found by using the formula

d is the distance
t is the time taken
From the question we have

We have the final answer as
<h3>6 m/s</h3>
Hope this helps you
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