Some 2.5million people currently live in the sahara most of these in egypt mauritania morocco and algeria

true of false?

This is a true statement!

For example, the biggest city in the Sahara (admittedly placed on the edge of it, on the Atlantic coast) is Nouakchott, the capital of Mauritania - it has 1 million people, so a great portion of the 2.5 million.
Another big city is Ghardaia in Algeria - of 100 000 people. 

Nigeria and south africa

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