5.
Having access to a major river like the Red River helps an area's economy by

There don't seem to be any options so I'll list the general ways major rivers can contribute to an economy.

Transport - Major rivers can be a source of transport for goods to and from an area. This will contribute to an area becoming a centre of trade that can boost the economy of the area. Agriculture - Major rivers are good for farming as they can be used to water crops even when there is no rain as major rivers are not seasonal. The river can also bring fertile soil to the area which will also contribute to agriculture. Rivers can also help with fish farming which the locals can do to earn revenue. Recreation/ Tourism - Major rivers can also be a source of revenue in terms of tourism. People might want to come and see more of the river and so will visit. People there can capitalize on this by offering recreational activities as well as accommodation and selling of goods and services. Electricity - Major rivers can be a source of energy as well in the form of hydro-electricity. With major rivers, dams like the Aswan Dam in Egypt which use the Nile can be used to generate hydroelectricity as a cheaper alternative to thermal power.