18 What is this passage mainly about?
(A)How to get pure water.
(B)How to restore the soil and plants.
(C)How to turn a wasteland into a self-sufficient town.
(D)How to create sustainable living areas in cities.

Gaviotas, a rural鄉村 area in Colombia, is an example of how even desolate荒涼 places in the countryside can be developed for sustainable可持續 uman use.

This area had been considered a wasteland: dry brown savannah（尤指非洲等熱帶國家的）稀樹草原, without enough water, plant, or animal life to support a town.

But today a green spot of a 25,000-acre forest and big aluminium鋁 sunflowers begin to dot the empty savannah（尤指非洲等熱帶國家的）稀樹草原.

Under the trees are low white buildings and colorful houses, all with solar collectors.

Begun in 1971 as a scientific experiment, Gaviotas is now a self-sufficient town of 200, supported by clean, renewable industries.

In the beginning of restoring the unproductive savanna to a place where humans can live well, the first problem was finding pure water.

The Gaviotans invented a special kind of hand pump to reach deepwater reservoirs水庫.

Another goal was to restore the soil and plants.

After years, they discovered that Caribbean加勒比海 pines松樹 from Honduras could grow in the area’s thin, acidic酸性 soil.

As more people moved to Gaviotas, it was important to consider a pollution-free way of transportation.

Village mechanics工作, 技師 developed a bicycle especially designed for the area’s rough land.

Bicycles are now the official mode of transportation, cheap and pollution-free.

Gaviotas is a remarkable accomplishment成就；成績 of sustainable可持續 development.

This once dry landscape has been turned into a near paradise.