Explanation:

Answer(4) all of these.

Chad, the former French colony is now prime outpost of the West in fighting Islmamist militants across the Sahel. France still has a strong military presence in the sahel region. 
The Sahel part of Africa includes from west to east parts of northern Senegal, southern Mauritania, central Mali, northern Burkina Faso, the extreme south of Algeria, Niger, the extreme north of Nigeria, the extreme north of Cameroon and Central African Republic, central Chad, central and southern Sudan, the extreme north of South Sudan, Eritrea, and the extreme north of Ethiopia.