10. An inverted frustum of a cone, with an inner diameter at the base of 12 and a height of 18, is filled with water and then poured into another cylindrical container with an inner diameter at the base of 24. Assuming the container is sufficiently tall, the height of the water level in the cylindrical container is ( ).
(A) 1.5
(B) 3
(C) 4
(D) 4.5
(E) 6
10. A.

Let the height of the cylindrical container be $h$. Then
$$
\begin{array}{l}
\frac{\pi}{3} \times 12^{2} \times 18=\pi \times 24^{2} h \\
\Rightarrow h=\frac{12^{2} \times 18}{3 \times 24^{2}}=\frac{3}{2} .
\end{array}
$$