Foreshortening of an anatomic structure results in:

Foreshortening of an anatomic structure happens when the object is imaged at an angle rather than being perpendicular to the imaging receptor. As a result, the structure is projected onto the image receptor smaller than its actual size, leading to a misrepresentation of the true dimensions of that anatomy. This occurs due to the shape of the anatomy and the angle of projection, which causes parts of the object to appear compressed or shortened relative to their true length.

In this context, the other options do not accurately describe the effect of foreshortening. A structure cannot appear longer than its actual size under foreshortening; instead, it appears reduced. While geometric blur can occur due to motion or improper focus, it is not a direct effect of foreshortening itself. Magnification occurs when an object is closer to the imaging receptor, which is contrary to the effect of foreshortening, where the size on the receptor is diminished. Thus, the correct understanding of foreshortening directly supports the answer that it results in the projection of the anatomic structure being smaller than its true size.