(2009? Fengxian District, second model) as shown in the figure, lightweight bracket ABC, AB and AC with a smooth hinge connected at A, AC perpendicular to the ground, B, C, respectively, with a light

AB rod force is balanced, the combined moment is zero; the line of action of the tension force across the point B, the moment is zero; light rod, gravity is not counted; therefore, the moment of the force of the AC rod is zero;

AC rod is also balanced, the combined moment is zero; light rod, gravity is not counted; therefore, the moment of the force of the AB rod is zero;

AB and the AC rod of the interaction between the force of the equidistant, reversed, * * * line;

And AC rod between the interaction force is equal, reversed, * * * line;

And AC rod is equal, reversed, * * * line;

And AC rod is equal, reversed, * * * line. * line;

Therefore, the interaction force between AB and AC rod is zero, otherwise it is impossible for the moments to be zero at the same time;

Therefore, choose D.