3. Current fast radiographic film requires less than % of the initial exposure times used in 1920. a. 25 b. 10 c.5 d. 2 A B C o 4. The fundamental unit of matter is the a. Proton b. Neutron c. Electron d. Atom A B c D

3. **d. 2**<br /><br />Modern radiographic film is incredibly sensitive compared to early versions. It requires less than 2% of the exposure time needed in 1920.<br /><br />4. **d. Atom**<br /><br />While protons, neutrons, and electrons are subatomic particles *within* an atom, the atom itself is considered the fundamental unit of matter.<br />