Which of the following rivers is an inland drainage?

An inland drainage system is a type of river system that does not flow into the ocean or sea. Instead, the river water flows into a lake or an inland sea. Out of the four options given, the River Hadejia is an inland drainage system because it flows into the Hadejia-Nguru wetlands in northern Nigeria, which is an inland freshwater swamp. The river does not flow into any ocean or sea. The other three options, namely the River Nile, River Senegal, and River Volta, do not belong to the inland drainage system because they all flow into the Atlantic Ocean.