Which of these would produce a soft sound A (a slow vibration) B (a big vibration) C (a fast vibration) or D (a tiny vibration)

A slow vibration

Explanation:

Hard and soft refer to how much a sound vibrates. When a sound is hard the vocal cords come together and release producing a less resonant sound. In a soft sound, the vocal cords rub together creating friction and heat that results in a more resonant sound.

the answer would be a