What adjustment should be made to correct for magnification caused by the air-gap technique?

The adjustment to correct for magnification caused by the air-gap technique is to increase the Source-to-Image Distance (SID). By increasing the SID, you reduce the effect of magnification that occurs when using an air gap.

In radiographic imaging, magnification is influenced by the relationship between the Object-to-Image Distance (OID) and the SID. When the OID is increased, as is often the case in air-gap techniques, the size of the image on the receptor can appear larger than the actual object. To counteract this, increasing the SID helps to diminish the magnification effect. This occurs because a greater distance between the X-ray source and the image receptor helps to project the anatomical structures more accurately, reducing their apparent size.

While other options involve changing either the OID or the SID in the opposite direction, they would not effectively counteract the magnification as increasing the SID does. Increasing OID would further exaggerate the magnification effect, while decreasing SID could potentially increase magnification as well. Therefore, the optimal approach when using the air-gap technique is to increase SID to maintain the desired image quality.