答案：B
設 $w=\dfrac{kx^2}{y^3}$，其中 $k$ 為一非零常數。由此，可得
$\begin{array}{rcl}
w & = & \dfrac{kx^2}{y^3} \\
k & = & \dfrac{wy^3}{x^2} \\
\dfrac{1}{k} & = & \dfrac{x^2}{wy^3}
\end{array}$
