Which region in Africa has the most one-commodity countries?

Sub-Saharan Africa

Explanation:

One-commodity countries are defined as country that depend on one principle export for more earnings.

Sub-Saharan Africa in Africa has the most one-commodity countries where  89% of countries are there that are commodity-dependent. While other regions the Middle East and North Africa, only 65% of countries depend on commodities.

Hence, the correct answer is "Sub-Saharan Africa".