Concept:The gold leaf electroscope is used to detect and compare the relative magnitudes of charges on different bodies.
Explanation:A gold leaf electroscope has a metal rod with two thin gold leaves attached at its lower end inside a glass case.
When a charged body touches the metal rod, the charge flows to the gold leaves.
Both leaves receive like charges, so they repel each other and spread apart.
The degree of divergence of the leaves depends on the quantity of charge transferred.
A larger charge causes a greater angle of separation between the leaves.
Hence, by touching two different charged bodies to the electroscope one after another, their relative charge magnitudes can be compared by observing the leaf divergence.
An ebonite rod is used for charging by friction, a proof plane transfers small charge samples, and an electrophorus generates charge — none of these compare charge magnitudes.
Answer:Gold Leaf Electroscope (Option C).