The answer is D, the Nile River is the worlds' longest river. It is 4,258 miles long (6,853 kilometers) and flows through 11 countries including Tanzania, Uganda, Rwanda, Berundi, the Democratic Republic of the Congo, Kenya, Ethiopia, Eritrea, Sudan, South Sudan, and Egypt. It is the primary water source of Egypt and Sudan.
While the Nile River doesn't flow through the heart of the Sahara Desert, it flows through the northeastern part of the desert and has made the areas around it hospitable for forestation and agriculture, despite the desert conditions. In fact, satellite images show the growth of vegetation along the Nile river, while being surrounded by desert.
It also played an important role in the founding of Egyptian civilization. In other areas of the Sahara desert, it was difficult for civilizations to thrive because of the hot, dry conditions. The Nile allowed Egypt to have a productive agricultural based economy. The Nile often overflowed its banks, which made the land fertile. The Egyptians grew and traded wheat, flax, papyrus and other crops with its neighbors who depended on the crops. This helped Egypt to establish diplomatic relations and gave the civilization economic stability.
