Where is this city ???

This question was asked on Koun Banega Karodpati program.

Question 

Mbanza Congo which is the former capital of kingdom of Congo is situated in which country ???

Angola 

Democratic Republic of Congo

Republic of Congo

Gabon 

Answer 

Don't get deceived by the words  " capital of Kingdom of Congo "!!!

Because I had got and thought the nation Congo must be the answer.

But in options, there are two nations with Congo  in their name !!!

So which one is it ???

Most probably none of them.

So we are left with 2 countries 

Angola                        Gabon 

One of them should be the correct answer  !!!!

I have done some research for this.

Kingdom of Congo was a powerful kingdom that was ruled from 14 to 19 century.

Mbanza Kongo was its capital and the city played crucial role in trade , politics and spiritually.

Now the city is a UNESCO world heritage site.

It is in                        ANGOLA           !!!!!!!!