History: What is the most sensitive frequency range of human hearing?

What is the most sensitive frequency range of human hearing?

• 20 Hz - 15,000 Hz.
  This is the range we usually hear within.
• All equal.
  We do not perceive all frequencies evenly.
• 20 Hz - 20,000 Hz.
  This is the commonly cited range of human hearing.
• 1.5 kHz - 5 kHz.
  Correct!