How does a rubber rod become negatively charged through friction? It touches a negatively charged object, and protons move off of the rod. It touches a positively charged object, and electrons move onto the rod. It is rubbed with another object, and electrons move onto the rod. It is rubbed with another object, and protons move off of the rod.

The rubber is rubbed with another object and electrons move onto the rod.

Option C

Explanation:

The negative electrons on objects get transmitted on the rubber rod when it rubbed on the negative object. If you take the example of wool, it will be negatively charged. Because when the rod is rubbed on a wool certain amount of electrons will pass from wool to rod and it will become negatively charged, while positive protons will remain on wool. This called a 'law of conservation of electric charge'.

This can also happen with silk if you rubbed silk on rubber rod the rod will be negatively charged by the transmission of negative electrons from silk.