Kosovo declared its independence from Serbia.

Now let`s understand each option briefly -

Option 1: Bulgaria - This is incorrect because Bulgaria is a Balkan nation which is completely separate from Kosovo. Bulgaria itself is an independent nation with its own distinct history.

Option 2: Croatia - This option is false too. While Croatia, like Kosovo, is situated in the Balkans and was part of the former Yugoslavia. However, Kosovo was not a part of Croatia nor did it declare independence from it.

Option 3: Macedonia - Macedonia, just like Bulgaria and Croatia, is another separate nation located in the Balkan Peninsula. However, Kosovo`s independence was not declared from Macedonia.

Option 4: Serbia - This is the correct answer. Kosovo, an autonomously governed province within Serbia, declared its independence from Serbia in 2008 after a long history of conflict and tension. Therefore, the statement is accurate that Kosovo declared its independence from Serbia.