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?

The answer is Static Electricity. When you say static electricity, there is a certain imbalance in the particles present on the surface of the material. That is why the electroscope was able to detect static electricity from the piece of cloth and plastic rod