Which type of government is based on a system that includes a prime minister as head of government?

The parliamentary system is characterized by having a prime minister as the head of government, making it distinct in its structure and function. In this system, the executive branch derives its legitimacy from the legislature (parliament) and is accountable to it. The prime minister is typically the leader of the majority party in the parliament and is responsible for running the government, proposing legislation, and administering public policies.

This contrasts sharply with a monarchy, where a king or queen may hold power, whether absolute or constitutional, typically with little or no accountability to elected representatives in a parliamentary format. Fascism, on the other hand, is an authoritarian political ideology that centralizes power in a dictator and does not necessarily adhere to a parliamentary structure. Lastly, communism is an ideology that aims to establish a classless society and often involves a centralized government but does not specifically define a prime ministerial role within its structure. Thus, the hallmark of the parliamentary system's governance structure is its prime minister, making this answer the most accurate choice.