Which of the following will cause elongation of the object when the object is horizontal?

When an object is positioned horizontally and you need to achieve a proper representation of it in an imaging system, elongation can occur due to misalignment between the central ray (CR), the object being imaged, and the image receptor (IR).

In this case, angling both the CR and the image receptor allows for an adjustment that accounts for the geometry of the object being projected onto the IR. By angling the CR towards the object and the image receptor in a complementary manner, the projection will capture the object in a way that minimizes distortion. This dual angling impacts how the x-rays interact with the object and are recorded by the IR, creating a more proportionate representation.

If only the CR is angled while the IR remains flat, or if the object is tilted alone with the CR and IR fixed, you may still end up with distortion or elongation. Angling the IR by itself tends to maintain the position of the object directly beneath it, which may not effectively represent the object in its true size or shape. Therefore, the combination of angling both the CR and the IR is essential to accurately project the object without elongation.