Largest river in Nigeria.

**The reasoning** The **River Niger** is Nigeria's longest river at approximately **4,180 km total length** (though only about 1,400 km flows through Nigeria). It enters Nigeria from the northwest (from Niger Republic), flows southeast, then curves south through the country before emptying into the Atlantic Ocean through the Niger Delta. This makes it not only Nigeria's largest river by length, but also by volume and basin area. The principle here is **geographic scale** — we're measuring by length, drainage area, and water volume. **Why the wrong options tempt you** - **B (Benue)**: Nigeria's second-longest river and the Niger's largest tributary. Since it's prominent and flows through central Nigeria, students often confuse it with the largest. - **C (Cross River)**: Important economically (gives its name to Cross River State), but much shorter. - **D (Ogun)**: Significant in southwestern Nigeria, but only regional in scope. **Quick takeaway** Remember: **"Niger is NUMBER ONE"** — it's literally in our country's name because it's our most significant river system, giving life to the Niger Delta and connecting much of West Africa.