At the Berlin Conference, European powers agreed that, in order to claim part of Africa, a European power had to

Aestablish missions there to spread the Christian faith.
Bset up a government office there.
Cestablish businesses there.
Dconquer the ruling African tribes there.

Verified Answer :

At the Berlin Conference the principle of Effective Occupation was established, that said that a country needed to have an actual presence in the colony to be bale to claim it.

In practice, this meant at least c. establishing businesses there. Additionally, they could make contact and conquer the local rulers.