b
In fundamental mode, \(l=2\left(\frac{\lambda}{4}\right)=\frac{\lambda}{2}\)

\(\Rightarrow \lambda=2 l \ldots(i)\)

Given, \(l=100 cm , v=2.53 kHz =2.53 \times 10^{3} Hz\)

We know that,

\(v=v \lambda\)

\(=v \times 2 l\) [from equation \((i)]\)

\(=2.53 \times 10^{3} \times 2 \times 100 \times 10^{-2}\)

\(=5.06 \times 10^{3} m / s\)

\(=5.06 km / s\)