Why did the ming dynasty rebuild the great wall of china?

a. to keep out the vietnamese imvaders.
b. to keep out the japanese invaders.
c. to keep out mongol invaders.
d. to keep de korean invaders.

2. a land bridge connected asia and north america thousands of years ago.

4. crossing the land bridge would have been simple for the first migrants.

5. people might have crossed a land bridge while hunting animals.