History: What does the diaphragm in the speaker do?

What does the diaphragm in the speaker do?

• The diaphragm moves to match the analog signal, which creates changes in pressure in the air to create sound.
  Correct.
• The air molecules are spaced apart.
  This is rarefaction.
• The diaphragm moves to match the changes in air pressure, which is recorded and sampled in the digital converter.
  This is the diaphragm in the microphone.
• The air molecules are dense.
  This is compression.