In which of the following situations is photoelectric effect employed?

I. Automatic devices for switching on light at dusk

II. Automatic doors in departmental stores

III. Automatic devices for switching on air conditioners

IV. Automatic voltage stabilizers

• A Automatic devices for switching on light at dusk
• B I, II and IV only
• C I, III and IV only
• D III and IV only
• E I and II only