Answer: the rebuilding of the Great Wall
At that time, the Chinese citizens had to face constant threats from the barbarian that resided on the northern part of their territory.The previously built wall was not strong enough and able to be destroyed by the invaders. Ming Dynasty took the credit of rebuilding and strengthening the structure of the great wall.
"Steam engine" is the one invention among the choices given in the question that <span>was the basis for the major developments in American transportation. The correct option among all the options that are given in the question is the first option or option "a". I hope that this is the answer that has come to your help.</span>
Ships that were narrow and could navigate thin waterways. These ships were called battering ships because they would ram into other ships to sink them.
