D. March because it is just below the 1 million marker on the graph and it is the only one that low.
Answer: A
<u>Explanation:</u>
NOTES:
d = 650 meters
t = 10 seconds
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v = d/t
= 650 meters/10 seconds
= 65 meters/second
Length of the pipe = 0.39 m
Third harmonic frequency = 1400 Hz
For the third harmonic:
Wavelength = 
The center of the open pipe will host a node and the nearest anti - node from the center will be at the 0.25 × wavelength
Distance from center = 0.25 × wavelength
Distance = 
Plugging the value of the length of the pipe (L) = 0.39 m = 39 cm
Distance = 
Distance from the center to the nearest anti - node = 6.5 cm
Hence, the nearest distance to the anti - node from the center = 6.5 cm
So, option C is correct.