what force decreases the cross - sectional area of the structure incurring the load?\na) tension\nb)…

Brief Explanations:

Compression is a force that acts to reduce the volume of a material, which can lead to a decrease in the cross - sectional area of a structure under load. Tension stretches a material, torsion twists it, and shear causes layers of a material to slide relative to each other, none of which primarily decrease cross - sectional area like compression does.

Answer:

B. Compression