Which of these used to be a country but no longer exists?

So your ancestors are listed in records as “Prussian,” but you can’t find Prussia on modern maps of Europe. What gives? Before being absorbed into Germany, Prussia was a major military and economic power in Central Europe during the 18th and 19th centuries. Is Prussia the Same as Germany? Not exactly. At its peak, Prussia included half of modern Poland and all but southern Germany.

Source: Family Tree