Can we incorporate this reply into the paper? Something like:
The participants were permanent residents of Khartoum and indigenous to northern Sudan. None of them were refugees or migrants from other parts of the country. They came from lower, middle, and upper socioeconomic strata.
I don't really mind, but the problem is the following paragraph.
There was no information on the participants of this study in terms of social class or ethnic background. This may be a problem because of the social and ethnic heterogeneity of Khartoum state, particularly the large number of migrants, including refugees, from all parts of the country.
These two ideas cannot live together. One of these claims must be false. So, would you agree to delete this paragraph and replace it by the answer given by Bakhiet ? Personally, I think your suggestion is good. I will email him if you agree.