An electroscope is a device that detects charge on objects that touch it or are brought near it. John rubs a piece of cotton fabric on a plastic rod and then touches the rod to the electroscope. What methods of charging does John use?

Rubbing the cotton fabric on the plastic rod transfers electrons between the materials, charging the rod by friction. When John touches the rod to the electroscope, charge moves through direct contact, which is conduction. Therefore, the correct choice is A: friction followed by conduction.

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