The correct options are
A A single entity governs a sovereign state.
C Many unitary states have a local government system arrangement.
A unitary system of government or unitary state is a sovereign state governed as a single entity. The administrative divisions exercise only those powers that the central government has delegated to them. In many unitary states, there is a local government system arrangement and decentralisation of authority. There can be provincial councils and committees with significant power, but they still work within a Unitary Constitutional framework and cannot claim federal status.