Fact 1: Matter vibrating can cause sound.

Fact 2: Energy strikes the molecule, causing it to vibrate more vigorously.

Given the two facts above, answer the question "What striking a molecule can cause sound?" with the following options: 
- waves
 - thoughts
 - nerves
 - voltage
 - cells
 - instincts
 - energy
 - photons


 

       energy  