sentences: someone plays the flute & if a flute is played, then the air in the flute will vibrate -> the land in the 18 will vibrate when the hunt is played the air in the flute will vibrate when the flute is played  the land in the 18 will vibrate when the hunt is played & vibrations are a source of sound -> the vibrations of air in the flute are a source of sound when the flute is played