# A material B has twice the specific resistance of A. A circular wire made of B has twice the diameter of a wire made of A. Then for the two wires to have the same resistance, the ratio $\large\frac{l_A}{l_b}$ of their respective lengths must be
$\begin {array} {1 1} (A)\;2 & \quad (B)\;1 \\ (C)\;\large\frac{1}{2} & \quad (D)\;\large\frac{1}{4} \end {array}$