Research Question: "How did the Mongols gain, consolidate, and maintain power in
their empires

The Mongols increased communication throughout Eurasia by developing

this pony express-like system of weigh stations with horses and riders that

could quickly relay information. It was called the yam system and also

included these amazing bronze passports, which facilitated travel.  Another thing that travelled along the Mongol trade routes was cuisine.

According to the source of Natural History which I paraphrased:

"The Mongols had developed a composite bow made out of sinew and horn and were skilled at shooting it while riding, which gave them the upper hand against ordinary foot soldiers. A wood-and-leather saddle, which was rubbed with sheep’s fat to prevent cracking and shrinkage, allowed the horses to bear the weight of their riders for long periods and also permitted the riders to retain a firm seat. Finally, a sturdy stirrup enabled horsemen to be steadier and thus more accurate in shooting when mounted. A Chinese chronicler recognized the horse’s value to the Mongols, observing that by nature they are good at riding and shooting."

i believe your answer is d)

the foundation of greek city-states: following the fall of the mycenaean civilization in the 10th century bc, the area surrounding the empire went through its own mini dark ages. answer and explanation