To what degree did emperors of the Ming dynasty seek a closed-door policy or an open-door policy?

PLEASE HELP

Explanation:

The Ming dynasty really had a balance of open and closed-door policies because it started out very open; The Chinese sailed around the world, acquired new tributaries, brought back foreign goods.

cold

very very cold

nuclear fission produces the atomic bomb, a weapon of mass destruction that uses power released by the splitting of atomic nuclei the fighting in iwo jima and okinawa affected the allies' pacific strategy because truman decided to drop the atomic bomb on mainland japan.