A musician stands behind an instrument. She holds two sticks called "mallets" in her hands. The instrument has many rectangle-shaped bars called keys. Each one produces a different sound when the musician hits it with a mallet. What is this thing?
It might be a vibraphone. It’s large: usually over 4 feet long and around 3 feet tall. Its keys are made out of shiny metal, and each one has a tube called a resonator underneath. The vibraphone produces a smooth, mellow sound. It is often used in jazz music.
It might also be a marimba. It’s about as large as a vibraphone, and it has resonators too, but its keys are made of dark wood. It makes shorter, softer sounds.
Finally, it might be a glockenspiel. They're also sometimes called “bells” for short. It has thin metal bars and is played with small, hard mallets. Its sound is loud and high-pitched, and it has no resonators.

According to the passage, what are mallets?

(A) a type of xylophone


(B) musicians who pay instruments


(C) sticks used to play certain instruments


(D) a type of music