Concept:Nigeria's international boundary lengths determine which neighbouring West African country it shares the longest border with.
Explanation:Nigeria is bordered by four countries: Niger to the north, Benin to the west, Chad to the northeast, and Cameroon to the east.
Among these, the boundary between Nigeria and Niger is the longest, stretching approximately
1,497 kilometres across Nigeria's northern border.
In comparison, the Nigeria–Benin border is about
773 km, while the Nigeria–Chad border, shared mostly through Lake Chad, is far shorter.
Ghana does not share a direct land border with Nigeria, so it is not a valid option.
Because the question asks specifically about West African countries, Niger, which lies to the north of Nigeria, is the correct choice.
Answer:Nigeria shares its longest border with Niger (Option A).