The answer would be letter A.
radiation I believe that is it
It was "the Golden Horde" who undertook the task of conquering Russia, although it should be noted that many other groups have attempted to take this land in the past as well.
Answer:
In the 1330s, many natural disasters and plagues led to widespread famine, starting in 1331, with a deadly plague arriving soon after. Epidemics that may have included the plague killed an estimated 25 million Chinese and other Asians during the fifteen years before it reached Constantinople in 1347.