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.

a large number of desalination plants.

Explanation:

Hello! The United Arab Emirates actually has the largest artificially desalinated water reservoir in the world. The construction of the reserve began in 2002, has cost around $ 540 million and that's why they needed the gallons of water, to build the plants.

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the answer is option a.