Which country is home to the world's longest sandy beach?

Which country has a coastline along the Baltic Sea? Which country has the coastline along the Black Sea? Which country has the longest coastline in the world? Which country has a coastline on the Adriatic Sea? 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? Which country has a coastline on the Caspian Sea? Which of the following countries has a coastline on the Black Sea?