Which principle ensured that each province retained its own government after Confederation?

The principle that ensured each province retained its own government after Confederation is federalism. Federalism is a system of governance in which power is divided between a central authority and constituent political units, in this case, provinces. In Canada, the Constitution Act of 1867 established a federal structure that allowed provinces to have their own governments, enabling them to manage local affairs while still being part of a larger national framework.

This division of powers means that provinces can create and enforce their own laws on various matters such as education, health care, and transportation, tailored to their specific needs and conditions. The federal government handles national issues like defense and immigration, allowing for both local autonomy and cohesive national policies.

Unitary governance, in contrast, consolidates power within a single central government, which does not allow for the same level of regional autonomy as federalism. Republicanism emphasizes the role of elected representatives and the concepts of civic virtue and the common good, but it does not specifically address the division of powers between different levels of government. Monarchy pertains to a system of governance led by a king or queen and isn't relevant to the governing structure established by Confederation in Canada. Thus, federalism is the correct principle that guarantees provincial governments' independence and authority.