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.

When there are advances in technology, such as the personal computer, how might business productivity change? a) productivity is separate from technological advances so there is no impact. the new technology can replace outdated, less efficient, machinery. o) the businesses' products will no longer be demanded. d) manufactured items will be made elsewhere.