A loose union of independent states that unite for a common purpose (such as defense) is a= Federal system Constitutional government Confederation Unitary system

The correct answer is: Confederation.A confederation is a loose union of independent states that unite for a common purpose, such as defense. In a confederation, the central government has limited powers, and the individual states retain a high degree of sovereignty. The states in a confederation typically have their own governments and make decisions independently, with the central government having only those powers specifically granted to it by the states.