Which of these countries is not a federal state?

A federation (also known as a federal state) is a political entity characterized by a union of partially self-governing provinces, states, or other regions under a central federal government (federalism). Federations are often multiethnic and cover a large area of territory (such as Russia, the United States, Canada, India, or Brazil).

Angola is a country located on the west coast of Southern Africa. It is the second-largest lusophone (Portuguese-speaking) country in both total area and population (behind Brazil), and it is the seventh-largest country in Africa.

Since the adoption of a new constitution in 2010, the politics of Angola takes place in a framework of a presidential republic, whereby the President of Angola is both head of state and head of government, and of a multi-party system. Executive power is exercised by the government. Legislative power is vested in the President, the government and parliament.