The correct answer is A. It provided most of the water in the region.
Step-by-step explanation
The Nile River is the most important river on the African continent due to its extension, being the second-longest in the world after the Amazon River. The Nile River crosses ten countries that are Burundi, Egypt, Ethiopia, Kenya, Rwanda, Tanzania, Uganda, the Democratic Republic of the Congo, South Sudan, and Sudan, and in its northernmost part, it forms a delta that empties into the Mediterranean Sea. This river was decisive for the Egyptian civilization that occupied most of northwestern Africa including the Nubian region. The importance of this river for this civilization was that it allowed fertile lands to existing and provided most of the water that was used in the region for different uses such as construction, food, and cultivation. According to the above, the correct answer is A.