I think the answer is number3
The molecules in hot air are moving faster than the molecules in cold air. Because of this, the molecules in hot air tend to be further apart on average, giving hot air a lower density
three.
It is formed by the confluence of three other rivers, the White Nile (Bahr-el-Abiad), Blue Nile (Bahr-el-Azrak) and River Atbara. The Blue Nile (Bahr-el-Azrak) flows from Lake Tana (Ethiopia), converging with the White Nile in Khartoum, capital of Sudan
