high-kilovoltage exposure factors are usually reguired for radiographic examinations using

high-kilovoltage exposure factors are usually reguired for radiographic examinations using:
1. water-soluble iodinated media
2. anegative contrast agent
3. barium sulfate
a. 1 only
b. 3 only
c. 1 and 2 only
d. 1,2 and 3