lf Einstein’s photoelectric equation is represented by hf - W = Φ where h is Planck’s constant, f the frequency of incident radiation and W the work function of the material, what does the symbol Φ up stand for?

• A Energy of the photons
• B Maximum Kinetic energy of the ejected electrons
• C Threshold frequency of the photons
• D Stopping potential of the electrons
• E Velocity of the electrons