I’m pretty positive that it’s A. Conduction. Just refer to the definition of it.
Answer:
f'=5.58kHz
Explanation:
This is an example of the Doppler effect, the formula is:
Where f is the actual frequency, 
is the observed frequency, 
is the velocity of the sound waves, 
the velocity of the observer (which is negative if the observer is moving away from the source) and 
the velocity of the source (which is negative if is moving towards the observer). For this problem:
A scientific law is the simple mathematical expression of the relationship involved. A principle is the same relationship expressed in words. A theory is the explanation of the facts that make up the relationship.
Solar Radiation, Orbital Distance, Air Pressure, and the Abundance of water.
