Why have ethnic rivalries and communal violence been a major problem in decolonized African and Asian nations?

a. African and Asian societies were not developed at the time of colonization.

b. Westerners' introduction of slavery in the late 19th century led to African and Asian
dependency on Europeans for financial support.

c. African and Asian ethnic groups engaged in ongoing warfare prior to colonization.

d. Europeans established boundaries without consulting with ethnic groups and considering
cultural similarities.