The relationship between the resonant frequency of a pipe, the resonant wavelength of the pipe, and the speed of sound in air is
$\begin{align*}\lambda f = v\end{align*}$
where $\lambda$ is fixed by the length of the pipe. We are told that $v$ is decreased by $3 \%$ ; therefore, the new frequency is
$\begin{align*}\frac{440 \mbox{Hz} \cdot 0.97 v}{v} = 426.8 \mbox{ Hz}\end{align*}$
Therefore, answer (B) is correct.

Solution to 2001 Problem 50