D

Step 1: Understand the photoelectric effect. When light of sufficient frequency shines on a metal surface, it can eject electrons from that surface. The energy of the emitted photoelectrons depends on the frequency of the incident light and the work function of the metal.
Step 2: The emitted photoelectrons do not have the same kinetic energy or frequency. Instead, they can have a range of kinetic energies depending on the intensity of the light and the work function of the metal.
Step 3: The minimum energy required to emit the electrons is determined by the work function (Φ) of the sodium metal. The excess energy is converted into kinetic energy of the emitted electrons.
Step 4: Since the speeds of photoelectrons can vary from zero to a maximum (determined by the frequency of the incident light and work function), the correct answer is:
Therefore, Option D is correct: They have their speeds varying from zero to a certain maximum.