You are presented with the question "what do you strum to cause vibration?" and the following answer choices: 
- brass instruments
 - waves
 - nerves
 - mechanical
 - energy
 - sound waves
 - guitars
 - drums

Now knowing that plucking a string can cause that string to vibrate and plucked stringed instruments are the harp, guitar, and harpsichord, choose the best answer.


 

       guitars  