Which country has the longest coastline in the world?

Which country has the coastline along the Adriatic Sea? Which country has a coastline along the Persian Gulf? Which country has a coastline along the Baltic Sea? Which country has the coastline along the Black Sea? Which country has a coastline on the Adriatic Sea? Which country is home to the world's longest sandy beach? What is the name of the bay that borders the city of Rio de Janeiro? Which of the following countries does not have a coastline on the Baltic Sea?