a
We have \(v=v \lambda\)

or \(\lambda=\frac{\mathrm{v}}{\mathrm{v}}=\frac{340 \mathrm{m} / \mathrm{s}}{340 \mathrm{Hz}}=1 \mathrm{m}\)

First resonating length,

\(l_{1}=\frac{\lambda}{4}=\frac{1}{4} \mathrm{m}=25 \mathrm{cm}\)

second resonating length,

\(l_{2}=\frac{3 \lambda}{4}=\frac{3 \times 1 \mathrm{m}}{4}=75 \mathrm{cm}\)

Third resonating length,

\(l_{3}=\frac{5 \lambda}{4}=\frac{5 \times 1 \mathrm{m}}{4}=125 \mathrm{cm}\)

So third resonance is not possible since the length of the tube is \(120 \mathrm{cm}\).

Minimum height of water necessary for resonance \(=120-75=45 \mathrm{cm}\)