What is the purpose of using the auto-brightness feature on a mobile device with an LCD screen?

What is the purpose of using the auto-brightness feature on a mobile device with an LCD screen?

• to conserve battery power
• to reduce the interference from sunlight
• to prevent the burn-in effect on the screen
• to display text messages with better contrast
  

  Explanation: The LCD screen for most mobile devices uses the most battery power. Lowering the brightness or using the auto-brightness feature helps conserve battery power.