Answer:
A. The speed of the wave increases four times.
I believe you are correct, it is B: Diagnostic Services.
Diagnostic services are services like the staff at hospitals and the people who run machines that are related to medical needs.
<em>If this is incorrect, please, don't refrain to tell me.</em>
Answer:B)439.21 Hz
Explanation:
Given
velocity of train 
frequency of train 
speed of sound 
frequency from Doppler effect can be calculated by





Answer:a woman with a load on
her head and stationary
Explanation:
a woman with a load on her head and stationary.since distance is not covered work is not done