Unicameral legislatures are popular in
unitary system
federal system
confederal
rigid system
Correct answer is A
In government, unicameralism (Latin uni, one + camera, chamber) is the practice of having one legislative or parliamentary chamber. Thus, a unicameral parliament or unicameral legislature is a legislature which consists of one chamber or house.
A unitary state is a state governed as a single power in which the central government is ultimately supreme. The central government may create administrative divisions. Such units exercise only the powers that the central government chooses to delegate. Although political power may be delegated through devolution to local governments by statute, the central government may abrogate the acts of devolved governments or curtail their powers. A large majority of the world's states have a unitary system of government and adopt a unicameral legislature (of a legislative body having a single legislative chamber.)