11. (4 points) The perimeter of a rectangle is 48 cm, and it is known that the length is twice the width. The length of the rectangle is ( )
A. 8 cm
B. 16 cm
C. 24 cm
【Solution】Solve: $48 \div 2 \div(1+2) \times 2$
$$
\begin{array}{l}
=24 \div 3 \times 2 \\
=16 \text { (cm) }
\end{array}
$$

Answer: The length of the rectangle is 16 cm.
Therefore, the correct choice is: B.