This river brought diamonds to the namib desert. nile orange zambezi limpopo

Option: Orange River

Explanation:

The Orange River brought diamonds to the Namib Desert. The river is called the river of diamonds. Stones carried through the delta, which deposits in the river bed and banks. Several diamond mines have access to operate along this stretch. The river played a significant role in the South African during diamond rush when the first diamonds were found in the deposits of the alluvial soil in the orange.

81 is a composite number.