Final answer:
The lasting impact of new imperialism on Africa was political instability due to arbitrary borders imposed by European powers, resulting in starker ethnic divisions and violent ethnic conflicts.
Step-by-step explanation:
The lasting impact that new imperialism had on Africa was A. Political instability.
European powers imposed arbitrary borders, which split up existing kingdoms, tribes, and cultures, leading to political instability. The borders created by the imperialists often caused starker ethnic divisions and resulted in violent ethnic conflict. These effects of imperialism lasted long after independence, and many African countries still face political instability today.