Q: Fact 1: Plucking a string can cause that string to vibrate. Fact 2: Nylon string is by far the softest sound on the guitar. Given the two facts above, what do guitars make sound with?

Choices:
(a). friction;
(b). vibration;
(c). voltage;
(d). energy;
(e). power;
(f). bamboo;
(g). mechanical;
(h). heat energy;
A:
(b).