$23 \cdot 34$ is the base area of a rectangular box, the areas of the side, and the front are all known, the product of these areas equals
(A) the volume of the box.
(B) the square root of the volume.
(C) twice the volume.
(D) the square of the volume.
(E) the cube of the volume.
[Solution] Let the length, width, and height of the box be $x, y, z$, respectively. Then the areas of the sides of the box are $x y, y z, z x$.
From $x y \cdot y z \cdot z x=(x y z)^{2}$, we know that it is the square of its volume.
Therefore, the answer is $(D)$.