In a photoelectric effect experiment at a frequency above cut ***, the stopping potential is proportional to:
A. the energy of the least energetic electron before it is ejected
B. the energy of the least energetic electron after it is ejected
C. the energy of the most energetic electron before it is ejected
D. the energy of the most energetic electron after it is ejected
E. the electron potential energy at the surface of the sample
