Each piece of a partitioned system is called a subsystem, such as the political parties in a multiparty system.
When a system is partitioned into pieces, each piece is referred to as a subsystem. The correct answer is b. subsystem. For example, in a multiparty political system, each political party could be considered a subsystem within the larger system of political governance. In contrast, a single-party system would not have this kind of internal partitioning as it is dominated by only one political party.