An opera singer breaks a crystal glass with her voice. Which best explains why this occurs?

Question

The pitch of her voice matches the pitch of the glass.
The amplitude of her voice heats the glass until it breaks.
The intensity of her voice produces a standing wave in the glass.
The frequency of her voice matches the natural frequency of the glass.

Answer 1

The correct explanation for why an opera singer can break a crystal glass with her voice is:

The frequency of her voice matches the natural frequency of the glass.

This phenomenon occurs due to resonance. When the singer produces a sound at the same frequency as the natural frequency of the glass, it causes the glass to vibrate more intensely, eventually leading to its breaking point.