Europeans usually obtained slaves in Africa by which method?
A) promising them freedom if they worked in America
B) defeating their kingdom in battle
C) killing their leaders
D) buying them

D. Buying them.

Explanation:

The Trans-Atlantic Slave Trade flourished between 1450 and the end of the 19th century. European traders - Portuguese, Spanish, French, English, Dutch - arrived in their ships and bought local men, women and children. They could also organized campaigns to hunt for slaves in the area, or bought people from local merchants and rulers.  The local kings or lords in West Africa were actively involved in selling his own people as slaves for the large profitability of it.

battle of saint-mihiel, (12–16 september 1918), allied victory and the first u.s.-led offensive in world war i. the allied attack against the saint-mihiel salient provided the americans with an opportunity to use their forces on the western front en masse.

explanation:

the first historical instance of china engaging in internationalism was during the han dynasty.[1] at the start of the han dynasty, the huns in the north were attacking the frontiers of han and trying to obtain riches. emperor wu of han wanted to gain an alliance with a country called dayuezhi so the two countries could join together and fight against the huns.[2] to obtain this alliance, emperor wu sent zhang qian to the west to establish economic and cultural connections.[2] history records that during the han dynasty there were four primary avenues of contact between china and europe. they included the northern land route, the central land route, the southern sea route, and the far southern sea route.[1] the most famous of these routes is the central land route, or the classical silk road, comprising a network of roads stretching from northwest china to the ports of syria and the black sea, which passed through the oasis of the turkestans and northern persia.[1] the silk road was significant for chinese emperors because it provided dominance over central asia by developing resources and provided new markets for the export of china's most valuable resources.[1]