9. Given that the volumes of two cylinders are the same, the radius of the second cylinder is $10 \%$ more than that of the first cylinder. Which of the following statements is correct? ( ).
(A) The second cylinder is $10 \%$ lower than the first cylinder.
(B) The first cylinder is $10 \%$ higher than the second cylinder.
(C) The second cylinder is $21 \%$ lower than the first cylinder.
(D) The first cylinder is $21 \%$ higher than the second cylinder.
(E) The height of the second cylinder is $80 \%$ of the height of the first cylinder.
9. D.

Let the radius of the first cylinder be $r_{1}$, and the radius of the second cylinder be $r_{2}$. Then, according to the problem,
$$
\begin{array}{l}
\frac{r_{2}}{r_{1}}=\frac{11}{10} . \\
\text { Also, } \pi r_{1}^{2} h_{1}=V_{1}=V_{2}=\pi r_{2}^{2} h_{2} \\
\Rightarrow \frac{h_{1}}{h_{2}}=\frac{r_{2}^{2}}{r_{1}^{2}}=\frac{121}{100} \\
\Rightarrow h_{1}=1.21 h_{2} .
\end{array}
$$

Therefore, the first cylinder is $21\%$ taller than the second cylinder.