What development allowed russia to send sailing vessels to the remotest oceans

Leet, apparently, was not completed, as Russia stood on the brink of war with the Rzeczpospolita over Ukraine and Belarus, but the naval campaigns of the Cossacks were nevertheless a remarkable phenomenon in the history of the fleet, demonstrating the high level of martial skill possessed by the Russian and Ukrainian people. 

***The Caspian Sea also became a theater for campaigns of the Don and Yaik (Ural) Cossacks. The most courageous of the Cossack expeditions in the Caspian Sea is the well-known Persian campaign of Stepan Razin, which was begun in March of 1668. The Cossack fleet comprised 24 boats. The Cossacks moved along the western shore of the Caspian Sea to the Terek delta, where Razin was joined by Ataman Sergey Krivoy. From there, the Cossacks headed to Derbent, Baku and further south. Passing the winter on the Miyan-Kala Peninsula, they marauded the eastern shores of the Caspian, afterwards retreating to the isle of Suina, near the mouth of the Kura, where they destroyed a joint fleet of Persians and Kumyks, comprised of 70 vessels, and c

Both the han and the roman empire decline as a result of social unrest during their collapse.

The answer is the third one or c