Why Did the Pax Mongolica Come to an End

Why did the Pax Mongolica come to an end?

A) Conflict between various components of the Mongol Empire increased.
B) The Mongols lost control of the Silk Road to the Chinese.
C) The Mongols began to push further west into Europe and war broke out.
D) The Mamluk sultanate of Egypt began attacking caravans on the Silk Road.
E) The Mongols converted to Eastern Orthodox Christianity and so closed the Silk Road to Western Roman Catholics.