The government of one of the following countries operates an unwritten constitut...

This question is asking about which country operates with an unwritten constitution. An unwritten constitution means that there is no single written document that outlines the fundamental principles and laws of the country. Instead, the constitution is made up of various written and unwritten sources.

The options given are the Union of Soviet Socialist Republics, the United Kingdom, the United States, and Post-Apartheid South Africa. The correct answer is option B, the United Kingdom.

The United Kingdom operates with an unwritten constitution, which is made up of various sources including statutes, common law, conventions, and traditions. This means that there is no single written document that outlines the fundamental principles and laws of the country.

It is important to note that while the United States and Post-Apartheid South Africa also have written constitutions, they also have other sources of constitutional law. The United States has a constitution that is primarily based on a single written document, but it also includes various amendments, statutes, and court decisions. Post-Apartheid South Africa has a constitution that is primarily based on a single written document, but it also includes customary law and court decisions.

In conclusion, the correct answer to this question is option B, the United Kingdom, which operates with an unwritten constitution.