Question

the united arab emirates was able to use over 600 billion gallons of water in 2004 by building
a large port system to trade oil for water.
a large system of irrigation pipes.
a large number of desalination plants.
a large number of dams to store water.

Explanation:

The UAE is an arid region with limited freshwater sources. Desalination plants convert saltwater from the ocean into usable freshwater, which is the primary method the country uses to meet large-scale water demands. The other options are not feasible: trading oil for water would not meet such a massive volume need, irrigation pipes distribute water but don't create it, and dams are ineffective due to low rainfall.

Answer:

a large number of desalination plants.