Please answer the following question: Information:  - The Ottoman Empire ('; Modern Turkish: ' or '), also known as the Turkish Empire, Ottoman Turkey, was an empire founded at the end of the thirteenth century in northwestern Anatolia in the vicinity of Bilecik and Söüt by the Oghuz Turkish tribal leader Osman. After 1354, the Ottomans crossed into Europe, and with the conquest of the Balkans the Ottoman Beylik was transformed into a transcontinental empire. The Ottomans ended the Byzantine Empire with the 1453 conquest of Constantinople by Mehmed the Conqueror.  - Romania is a sovereign state located in Southeastern Europe. It borders the Black Sea, Bulgaria, Ukraine, Hungary, Serbia, and Moldova. It has an area of and a temperate-continental climate. With 19.94 million inhabitants, the country is the seventh-most-populous member state of the European Union. The capital and largest city, Bucharest, with its 1,883,425 inhabitants is the sixth-largest city in the EU.  - Oltenia is a city in Romania in the Clrai County on the left bank of the Arge River where its waters flows into the Danube.  - The Battle of Turtucaia ( Bulgarian :    , Bitka pri Tutrakan or Bulgarian :   , Tutrakanska epopeya ) in Bulgaria , was the opening battle of the first Central Powers offensive during the Romanian Campaign of World War I. The battle lasted for five days and ended with the capture of the fortress of Tutrakan ( Turtucaia in Romanian ) and the surrender of its Romanian defenders .  - Silistra (pronounced ) is a port city in northeastern Bulgaria. The city lies on the southern bank of the lower Danube river, and is also the part of the Romanian border where it stops following the Danube. Silistra is the administrative center of the Silistra Province and one of the important cities of the historical region of Southern Dobrudzha.  - Turkey, officially the Republic of Turkey (Turkish: ), is a transcontinental country in Eurasia, mainly in Anatolia in Western Asia, with a smaller portion on the Balkan peninsula in Southeast Europe. Turkey is a democratic, secular, unitary, parliamentary republic with a diverse cultural heritage. Turkey is bordered by eight countries: Greece to the west; Bulgaria to the northwest; Georgia to the northeast; Armenia, the Azerbaijani exclave of Nakhchivan and Iran to the east; and Iraq and Syria to the south. The Aegean Sea is to the west, the Black Sea to the north, and the Mediterranean Sea to the south. The Bosphorus, the Sea of Marmara, and the Dardanelles, which together form the Turkish Straits, divide Thrace and Anatolia; they also separate Europe and Asia. Turkey's location has given it geopolitical and strategic importance throughout history.  - Serbia, officially the Republic of Serbia, is a sovereign state situated at the crossroads of Central and Southeast Europe, covering the southern part of the Pannonian Plain and the central Balkans. Relative to its small territory, it is a diverse country distinguished by a "transitional" character, situated along cultural, geographic, climatic and other boundaries. Serbia is landlocked and borders Hungary to the north; Romania and Bulgaria to the east; Macedonia to the south; and Croatia, Bosnia-Herzegovina, and Montenegro to the southwest; it also claims a border with Albania through the disputed territory of Kosovo. Serbia numbers around 7 million residents, and its capital, Belgrade, ranks among the largest cities in Southeast Europe.  - The Central Powers , consisting of Germany, , the Ottoman Empire and Bulgaria  hence also known as the Quadruple Alliance  was one of the two main factions during World War I (191418). It faced and was defeated by the Allied Powers that had formed around the Triple Entente, after which it was dissolved.  - The Black Sea is a body of water between Eastern Europe and Western Asia, bounded by Bulgaria, Georgia, Romania, Russia, Turkey, and Ukraine. It is supplied by a number of major rivers, such as the Danube, Dnieper, Rioni, Southern Bug, and Dniester. The Black Sea has an area of (not including the Sea of Azov), a maximum depth of , and a volume of . It is constrained by the Pontic Mountains to the south and by the Caucasus Mountains to the east, and features a wide shelf to the northwest. The longest east-west extent is about .  - Greece (' ), officially the Hellenic Republic (Greek: ' ), historically also known as Hellas ("" ), is a country in southeastern Europe.  Greece's population is approximately 10.955 million as of 2015. Athens is the nation's capital and largest city, followed by Thessaloniki.  - Bulgaria (tr. '), officially the Republic of Bulgaria (tr. '), is a country in southeastern Europe. It is bordered by Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, and the Black Sea to the east. With a territory of , Bulgaria is Europe's 16th-largest country.  - Southern Dobruja (Bulgarian:  , "Yuzhna Dobrudzha" or simply , "Dobrudzha") is an area of north-eastern Bulgaria comprising the administrative districts named for its two principal cities of Dobrich and Silistra. It has an area of 7,565 km² and a population of 358,000. When it was a part of Romania from 1913 to 1940 it was known in Romanian as "Dobrogea de sud", the "Cadrilater" ("Quadrilateral"), or "Dobrogea Nou" ("New Dobruja").  - The Triple Entente (from French "entente" "friendship, understanding, agreement") was the understanding linking the Russian Empire, the French Third Republic, and the United Kingdom of Great Britain and Ireland after the signing of the Anglo-Russian Entente on 31 August 1907. The understanding between the three powers, supplemented by agreements with Japan and Portugal, constituted a powerful counterweight to the Triple Alliance of Germany, Austria-Hungary and the Kingdom of Italy, though Italy did not side with Germany and Austria during World War I, and joined the Entente Powers instead, in the 1915 Treaty of London.  - Silistra Province (transliterated "Oblast Silistra", former name Silistra okrug) is a province of Bulgaria, named after its main city - Silistra. It is divided into seven municipalities with a total population, as of December 2009, of 127,659.  - Tutrakan is a town in northeastern Bulgaria, an administrative centre of the homonymous municipality, part of Silistra Province. It is situated on the right bank of the Danube opposite the Romanian town of Oltenia (to which it was linked through a ferry but the ferry does not work anymore), in the very west of Southern Dobruja, 58 km east of Rousse and 62 km west of Silistra. As of December 2009, the town has a population of 9,476 inhabitants.  - The Danube (, known by various names in other languages) is Europe's second-longest river, after the Volga River, and also the longest river in the European Union region. It is located in Central and Eastern Europe.  - A ferry is a merchant vessel used to carry passengers, and sometimes vehicles and cargo as well, across a body of water. Most ferries operate regular return services. A passenger ferry with many stops, such as in Venice, Italy, is sometimes called a water bus or water taxi.    After reading the paragraphs above, choose the best answer for the entity that related to 'battle of turtucaia' with the relationship of 'location'.  Choices: - aegean sea  - anatolia  - asia  - athens  - bank  - belgrade  - black sea  - bosnia  - bulgaria  - center  - central  - constantinople  - croatia  - eastern europe  - europe  - germany  - greece  - iran  - iraq  - ireland  - italy  - japan  - macedonia  - mediterranean sea  - ottoman empire  - portugal  - romania  - russia  - russian empire  - serbia  - southeast europe  - southern dobruja  - syria  - turkey  - united kingdom  - venice
A:
southern dobruja