The correct answer is B. In China the Mongols took over the government. In Russia Mongols allowed princes to rule for them.
One factor which led to fall of Mongol empire was that, Mongol struggled to govern enormous empire which was very impossible.
After Mongol took over China, Beijing became its capital city. The big part of Europe was not ruled by Mongol empire.
Mongol emerged from different nomadic tribes which were unified in homeland of Mongol. It stretched to sea of Japan from Central and Eastern parts. Their leader was Genghis Khan.
