The correct options are
A The fundamental frequency of vibration of this pipe is 1700 Hz.
B 11 is the highest harmonic of such tube in audible range.
C 6800 Hz is the third overtone frequency.
Given that,
Length of pipe, L=10 cm or 0.1 m
Speed of sound, v=340 m/s
Mode of vibration of air column in an open organ pipe is given by
fn=nv2L where n=1,2,3...
Fundamental frequency, f1=v2L
From the data given in the question,
f1=3402×10×10−2=1700 Hz
For maximum audible frequency,
fn=20000 Hz
So
fn=nv2L
⇒n=20000×2×0.1340=11.76≃11
For third overtone or fourth harmonic,
f4=4v2L=4×3402×0.1=6800 Hz
Thus, options (a) , (b) and (c) are the correct answers.