Answer:
option D
Step-by-step explanation:
given,
length of the pipe, L = 0.96 m
Speed of sound,v = 345 m/s
Resonating frequency when both the end is open

n is the Harmonic number
2nd overtone = 3rd harmonic
so, here n = 3
now,

f = 540 Hz
The common resonant frequency of the string and the pipe is closest to 540 Hz.
the correct answer is option D