atoms electrons neutrons protons
I gave my students this multiple choice question: Roberto is sliding down a plastic slide on the playground. After he reaches the ground, he feels a small electric shock when he touches a piece of metal. What has been built up on his body that causes the shock?

Only one answer is correct among these 4 choices:
- atoms
- electrons
- neutrons
- protons

Could you tell me which one is correct?

electrons