9. Person A and Person B both have a pet cat. Person A bought a cylindrical can of cat food with a base radius of 6 cm and a height of 12 cm, while Person B bought a cylindrical can of cat food with a base radius of 12 cm and a height of 6 cm. The volume ratio of the cans bought by Person A and Person B is $(\quad)$.
(A) $1: 4$
(B) $1: 2$
(C) $1: 1$
(D) $2: 1$
(E) $4: 1$
9. B.

Given the volume of a cylinder is $\pi r^{2} h$, the volume ratio of the cans of person A and person B is
$$
\frac{\pi r_{1}^{2} h_{1}}{\pi r_{2}^{2} h_{2}}=\frac{6^{2} \times 12}{12^{2} \times 6}=\frac{6}{12}=\frac{1}{2} .
$$