Concept:A device that stores electrical energy by holding equal and opposite charges on two conducting plates separated by an insulator is called a capacitor.
Explanation:When two flat plate conductors are placed parallel to each other and given equal and opposite charges, an electric field is created between them.
If a dielectric material (an insulating substance) is inserted between the plates, it reduces the effective electric field and increases the charge storage capacity.
This arrangement of two conductors separated by a dielectric is the basic construction of a capacitor.
An electroscope detects charge, an electrophorus is a manual charge-generating device, and a cell converts chemical energy into electrical energy.
None of these match the described setup of two charged plates with a dielectric.
Therefore, the arrangement forms a capacitor.
Answer:C. capacitor