For an AP-PA large intestine projection (lateral decubitus position),

1. uniform density is obtained by positioning the thick end of the compensating filter toward the imaging table.
2. an arrow or word marker is placed on the IR to indicate the side positioned adjacent to the imaging table.
3. the shoulders, posterior ribs, and posterior pelvis are positioned at equal distance to the imag-ing table.
4. the central ray is centered to the midsagittal plane at the level of the iliac crest.
a. 1 and 4 only
b. 2 and 3 only
c. 4 only
d. 1, 2, 3, and 4

C