high-kilo voltage exposure factors are usually required for radiographic examinations using.. barium sulfate

high-kilo voltage exposure factors are usually required for radiographic examinations using:
1. water-soluble iodinated media
2. a negative contrast agent
3. barium sulfate
a. 1 only
b. 3 only***
c. 1 and 2 only
d. 1,2 and 3