Angola’s economy is promising because of its .

oil exports

Explanation:

"Angola" is a country in South Africa. Its economy is considered to be one among the fastest-growing economies in the world. Majority of its economic success can be linked to the revenue which the country receives for its oil exports. The country's oil reserve is vast and this leads to an overall increase in oil production, that is even expected to grow in the coming years.

So, this explains the answer.