Concept:A confederal system is an association of states that come together under one common authority while retaining their identity and sovereignty.
Explanation:A confederal system is best described as a union of states with a common recognised authority.
Independent states deliberately agree to form such a union for purposes like defence or foreign affairs.
They then recognise the same central authority to act on behalf of all member states.
This arrangement is different from a federal system, where powers are constitutionally shared between a central government and component states within one country.
It is also different from a unitary system, where a single central government holds supreme power.
A representative system only concerns how leaders are chosen, so it does not describe a union of states.
Therefore, the correct option is the confederal system.
Answer:D. confederal system.