Concept:The ECOWAS passport is a joint travel document that simplifies border crossing for West African citizens.Explanation:ECOWAS introduced this passport to ease travel between its member countries.It reduces visa restrictions and immigration delays within the sub-region.The main goal is to allow citizens to move freely across borders with less hassle.Thus, it directly supports the free movement of people among member states.Answer:C. Free movement of people in the sub-region