Which of the following is not a source of a country's constitution?

A writ of Mandamus is not a source of a country's constitution. A writ of Mandamus is a court order that directs a government official to perform a specific duty. On the other hand, a country's constitution is a set of fundamental principles and rules that govern a nation. The sources of a constitution may include legislative decisions, past constitutions, and judicial precedents. However, a writ of Mandamus is not a source of a constitution as it is a legal remedy used to enforce existing laws and regulations rather than to establish new constitutional principles.