Air-Fluid Levels on an AP Chest Projection

Multiple Choice

Air-fluid levels on an AP chest projection
1) demonstrate an increase in density where the fluid is present.
2) are formed when air and fluid separate.
3) are precisely demonstrated when the patient is in a partially upright position.
4) are precisely demonstrated when the central ray is horizontal.

A) 1 and 3 only
B) 1, 2, and 4 only
C) 2 and 4 only
D) 2, 3, and 4 only