The answer is A. Black sea! hope this helps!
Euclid was ancient Greek mathematician, often referred as "father of geometry". His most important achievement was that he deduced the principles of what is now called Euclidian geometry from a small set of axiom. He did this in his best-known work named Elements. This was the most influential work in the history of mathematics. Although many of the results in Elements originated with earlier mathematicians, one of Euclid's accomplishments was to present them in a single, logically coherent framework. It contains a system of rigorous mathematical proofs which remained the basis for mathematics until today. He was active from 323 till 283 BC.
The steps they took were, ended fixed low prices for basic goods and services
The terms Tatars or Tartars are applied to nomadic Mongolic peoples who, themselves, were conquered by Mongols and incorporated into their horde. They were mainly composed of Kipchaks-Cuman people.
On October 28 [1480], Ivan gradually started to pull his armies back to Kremenets for winter quarters. Akhmat waited for reinforcements until November 11 and then turned south. Among other reasons for Akhmat's retreat was the possible threat of Crimean, Nogai or other attacks on his unprotected home base, a common problem in nomadic warfare. As Nikolai Karamzin wrote in his "History of Russian State", "It should have been an odd image: two armies ran away from each other, not pursued by anyone".
The Mongolian yoke over Russia was underpinned by their ability to compel obedience (i.e. tribute) through the force of arms. Akhmat Khan's retreat destroyed the credibility of this threat. Regardless of the actual circumstances, the fact that the Russians defied him and successfully withstood his retaliation, demonstrated the Horde no longer had the military strength to keep Russia subjugated.
So technically, the retreat wasn't the end of the yoke; that happened a few years earlier, when Ivan III stopped making tribute payments and repudiated Mongol authority. But the retreat confirmed it.
Of course, this wasn't a sudden shift. Muscovy had been gaining strength while the Horde slowly declined for over a century. As early as 1378, Dmitry ceased making regular tribute payments and fought off the Golden Horde's armies, though he submitted again in 1382. By 1480 Ivan III had consolidated most of Russia under his rule, while the Golden Horde had conversely fragmented into several successor states.
That said, 1480 does represent the last attempt by the Horde to re-assert its dominance over Russia. Accordingly, its dramatic failure is traditionally held to be the definitive end to the Tartar-Mongol yoke. Akhmat Khan's own death soon afterwards, as well as the Great Horde's destruction, sealed the deal.
