Fresh Water, Connected Sections

• ○A. It ranks the two separation methods by their effectiveness.
• ○B. It adds operating and environmental concerns to the technical explanation.
• ○C. It traces how the two separation methods were invented.
• ○D. It replaces the technical explanation with instructions for homeowners.

Successful separation does not settle every question about a desalination plant.Supplying heat or running high-pressure pumps uses energy, adding to the cost of the water.Operators also check the equipment regularly.Membranes, for example, need cleaning and eventual replacement.

• ○A. To introduce the contrast between abundant water and usable water
• ○B. To establish where the first desalination plant was built
• ○C. To compare coastal communities with inland communities
• ○D. To show that ocean water is already suitable for drinking

• ○A. Each describes a historical period, and the second explains a later invention.
• ○B. Each explains a method, and the second identifies differences and a shared result.
• ○C. Each ranks a water source, and the second identifies the preferred source.
• ○D. Each presents an objection, and the second answers the first objection.

• ○A. It introduces conservation as a substitute for separation.
• ○B. It returns to the opening scene to finish the introduction.
• ○C. It identifies a shared result that the next section examines.
• ○D. It concludes that the methods have equal operating costs.

• ○A. It shifts from plant operation to effects on the surrounding environment.
• ○B. It gives steps for replacing the equipment mentioned earlier.
• ○C. It explains why the two methods produce different kinds of salt.
• ○D. It contrasts the cost of pumps with the cost of heating water.

• ○A. It connects local rainfall to an explanation of how evaporation occurs.
• ○B. It connects the opening shortage to the history of water treatment.
• ○C. It connects membrane cleaning to a detailed maintenance schedule.
• ○D. It connects the preceding challenges to the consideration of other approaches.

• ○A. Local example → global statistics → regional comparison → personal reflection
• ○B. Past practices → recent discoveries → current debate → future predictions
• ○C. Water-supply problem → separation methods → practical challenges → broader planning
• ○D. Proposed solution → opposing opinions → experiment → final recommendation

• ○A. The examples of alternatives such as fixing leaking pipes
• ○B. The opening distinction between salt water and drinking water
• ○C. The explanation of how vapor can become liquid water
• ○D. The reasons that producing fresh water requires further planning

• ○A. Readers can use those challenges to calculate which method has the lowest energy cost.
• ○B. Readers can use those challenges to follow the steps for building their own membranes.
• ○C. Readers can use those challenges to understand why communities weigh several approaches.
• ○D. Readers can use those challenges to trace the historical spread of desalination plants.

• ○A. After paragraph 2, to expand the explanation of distillation
• ○B. After paragraph 5, to expand the discussion of environmental safeguards
• ○C. After paragraph 6, to expand the list of water-saving approaches
• ○D. After paragraph 1, to expand the opening water-supply contrast

• ○A. It returns to the larger supply question after explaining the factors involved.
• ○B. It replaces the earlier concern about reliability with a history of desalination.
• ○C. It narrows the earlier concern about supply to the movement of water molecules.
• ○D. It challenges the earlier supply question by showing that separation is unnecessary.