Explain simply why the District of Columbia is the correct answer to: Passage: Washington, D.C., formally the District of Columbia and commonly referred to as Washington or D.C., is the capital of the United States of America. Founded after the American Revolution as the seat of government of the newly independent country, Washington was named after George Washington, first President of the United States and Founding Father. Washington is the principal city of the Washington metropolitan area, which has a population of 6,131,977. As the seat of the United States federal government and several international organizations, the city is an important world political capital. Washington is one of the most visited cities in the world, with more than 20 million annual tourists.

Question: Based on this passage, what does the dc in washington dc stand for?. Explanation:
To answer the above question, the relevant sentence is: Washington, D.C., formally the District of Columbia and commonly referred to as Washington or D.C., is the capital of the United States of America.