X-rays are produced by firing electrons at a metal anode target. Which statement is correct?
A. The frequencies of the characteristic spectrum lines are determined by the potential used to accelerate the electrons.
B. The frequencies of the characteristic spectrum lines are determined by the metal used to make the target.
C. The maximum frequency of the braking radiation is determined by the metal used to make the target.
D. The minimum frequency of the braking radiation is determined by the potential used to accelerate the electrons.