Answer
To prevent the cable from snapping, $D$ should be increased to reduce the required tension in the cable.
Work Step by Step
We can consider the torque about a rotation axis at the hinge to find the vertical component $T_y$ of the cable's tension required to maintain equilibrium.
If $D$ decreases, then the tension in the cable would need to increase in order to maintain the same vertical component $T_y$ of the cable's tension required to maintain equilibrium.
Therefore, to prevent the cable from snapping, $D$ should be increased to reduce the required tension in the cable.
