Final answer:
Lack of breast compression is most likely to cause geometric unsharpness.
Step-by-step explanation:
Lack of breast compression is most likely to cause geometric unsharpness. Geometric unsharpness refers to the blurring or loss of detail in an image due to improper compression of the breast tissue during imaging. When breast compression is inadequate, it can lead to less image sharpness and reduced visibility of structures, making it difficult to accurately diagnose and interpret the image.