Which is the third most populous country in the world?

What is the most populous country in Oceania? Which country has the third-largest population in South America? What is the second most populous country in Southeast Asia? Which country is the most populous in West Africa? 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? What is the most populous country in the Commonwealth of Nations?