The byzantine traded with kiev Russia and they relied heavily on it, also leaders like Vladimir the 1 and Yaroslav brought Byzantine religion to kiev which became the basis for future Russia religion, art and culture.
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The Russians lived under Mongol rule for almost two centuries. During that time, the Mongol system was to place Vassal princes who were expected to pay tribute to the Mongols for the privilege of holding their own kingdom. The result was harsh rule that turned most Russians into serfs and destroyed the Russian economy, most importantly in regard to trade. Effects include halting Russia's technical development and relationships with other nations </span>Under the rule of vassal princes, the Russians were cut off from Europe and turned more toward the east in culture. The Russian language picked up words such as амбар, barn, and базар, bazaar from the Turkic languages. The architecture of St. Basil's Cathedral on Red Square has distinct Mongol and Eastern Styles. The dome shapes and use of tile may have been inspired by Kazan and the East.
Two hundred years of Mongol occupation in Russia influenced the development of Russian culture and economics.
I think its C because America enters the war when German started sinking there merchants ships.
The Missouri Compromise was an effort by Congress to defuse the sectional and political rivalries triggered by the request of Missouri late in 1819 for admission as a state in which slavery would be permitted. At the time, the United States contained twenty-two states, evenly divided between slave and free. i hope that helps you :)
The key victory of the Mexican war is when Winfield Scott went through Mexico and captured Mexico city.