How were the borders of many African countries established in the nineteenth century?

Boarders were established through fighting and trade, by the mid nineteenth century almost 90% or Africa was under European rule.

Side note:

When in doubt assume white men fought and took over

in an absolute  monarchy, the  monarchrules as an autocrat, with absolutepower  over the state and government — for example, the right to rule by decree, promulgate laws, and impose punishments. the  monarch isnominally sovereign but the electorate, through their legislature, exercise political sovereignty.

i would say b. research typically uses a variety of sources