Read the passage and choose the correct answer A, C, C or D.

Our future house will be on the ocean. It will be surrounded by tall trees and blue sea. But we only have salt water in the ocean. We need fresh water for ___(1)___ and for growing food ___(2)___ farms.
Ocean water is too salty ___(3)___. It is also too salty for watering plants. We must have the ___(4)___ to make fresh water from salty water. We should be ___(5)___ not to waste water.