6. In square $ABCD$, the distances from two vertices to line $l$ are equal and are twice the distances from the other two vertices to line $l$. How many such lines $l$ are there?
(A) 4
(B) 8
(C) 12
(D) 16
6. (C).

As shown in the figure, $A E=\frac{1}{2} E D, B F$ $=\frac{1}{2} F C$, then there are 8 such lines $l_{1}$. Also, the distance from $B, D$ to $l_{2}$ is twice the distance from $A, C$ to $l_{2}$, there are 4 such lines $l$, making a total of 12 lines.