Concept:The early European exploration of West Africa is associated with Mungo Park, a Scottish explorer who traced the Niger River on behalf of the British.
Explanation:Mungo Park led expeditions for the African Association.
He moved inland along the Niger, charted its course through West Africa, and reported on the region and its trade possibilities.
His published account made the river widely known in Europe.
That interest encouraged later British expeditions into the area that became Nigeria.
Therefore, the explorer credited with the "discovery" of the Niger River is Mungo Park.
However, Mungo Park is not among the options listed in the question.
The given names are linked to other regions:
James Cook and Ferdinand Magellan explored the Pacific.
John Cabot crossed the North Atlantic.
David Livingstone explored parts of southern and central Africa.
None of them is credited with the discovery of the Niger River.
Answer:The credited explorer is Mungo Park, so none of the provided options is correct.