Question

Most saltwater-use is to _____.

irrigate crops
provide the public with drinking water
manufacture products like tires and cars
generate electricity

Answer 1

Since all the other options seem ridiculous, I would say that most saltwater use is to generate electricity.
You cannot irrigate crops with salt water, it would destroy them.
You cannot provide the public with drinking water, because saltwater is not drinkable.
And how can you manufacture such products from water?

Answer 2

Most saltwater-use is to generate electricity. Since salt water naturally has electrolytes that can sustain in generating an electricity. This is also the reason why it is not advisable for people to swim in the ocean when it’s raining or there is a thunderstorm or visible lightning.