Which governmental structure involves a hereditary leader such as a king or queen?

The governmental structure that involves a hereditary leader, such as a king or queen, is known as a monarchy. In a monarchy, the position of the leader is typically passed down through family lines, meaning that the role is inherited rather than elected. This system has traditionally been characterized by a sovereign authority that often has substantial powers, although modern constitutional monarchies may limit the powers of the monarch through a constitution or legislative body.

In contrast, the other options represent different forms of government that do not focus on hereditary leadership. A parliamentary system features elected representatives who form the government, while a dictatorship is characterized by a single leader or party holding absolute power, often acquired via non-hereditary means. Socialism, meanwhile, primarily refers to an economic system where the means of production are owned or regulated by the community as a whole, and does not imply any specific method of leadership succession. Therefore, monarchy is distinct in its hereditary leadership aspect, which is why it is the correct answer.