In the 1700s and 1800s, nationalism in the Ottoman empire: created a strong sense of unity.

encouraged the empire to seek overseas colonies.

resulted in Ottoman expansion further into Europe.

led various ethnic groups to attempt to break away and form independent nations.

It is the last one

Explanation:

There was a lot of tensions between ottoman overlords and the peoples (other than Turks) that lived in the Empire. This was especially true at the Balkans in Europe. South slavic peoples (Serbs, Bulgarians, Macedonians), Greeks and Romanians mostly hated Ottomans, because they were foreign and of Muslim faith.