Explanation:

The sinking of the warship Moskva, the 600-foot, 12,500-tonne flagship of the Russian Black Sea Fleet is a serious setback for Russia. 

• The Black Sea is bound by Ukraine to the north and northwest, Russia and Georgia to the east, Turkey to the south, and Bulgaria and Romania to the west.
• It links to the Sea of Marmara through the Bosphorus and then to the Aegean through the Dardanelles.
• It has traditionally been Russia's warm water gateway to Europe.

Hence option 4th is correct.