What is the most populous country in the Commonwealth of Nations?

Which is the third most populous country in the world? Which country is the most populous in Central Europe? Which country has the largest population in Southern Europe? What is the most populous country in the European Union? Which country is the most populous in the Organization of American States? Which country is the most populous in the Baltic states? What is the most populous country in the Pacific Islands? Which country is home to over 210 million people and is the 5th most populous country?