Here's a problem to solve: Why does a plastic rod have a negative charge after being rubbed with a piece of fur?

Among the 4 following options, which is the correct answer?

- A: The fur gives up protons to the rod.
 
- B: The rod gives up electrons to the air.
 
- C: The fur gains protons from the rod.
 
- D: The rod gains electrons from the fur.
 