Directions: Read the passages below and select the best choices to complete the passages.
    Singapore’s average annual rainfall is more than (13)__________ of notoriously soggy Britain, (14)_________ the casual observer might be surprised to learn that the place has a shortage of drinking water. With around 7,000 people per square kilometer, Singapore is (15)________ densely populated country in the world. Its land mass is (16)______ its 5 million inhabitants with water.
    One answer is to desalinate seawater. That, though is expensive, so the Singaporean government is keen to find cheaper ways of doing it. And, (17)______ a German company, it may have done so, for the company says its demonstration desalination plant on the island can turn seawater into drinking water using less than half the energy required by the most effective previous method.
    (18)________ human consumption, its salt content of approximately 3.5% must be cut to 0.5%. (19)________ desalination plants do this in one of two ways. Some employ distillation, (20)________ needs about 10 kilowatt-hour of energy per cubic meter of seawater processed. Other plants employ reverse osmosis. This process needs about 4kWh per cubic meter. The new system, by contrast, consumes 1.8 kWh per cubic meter.