第三部分阅读理解（共20小题；每小题2分，满分40分）
阅读下列短文，从每题所给的A、B、C、D四个选项中，选出最佳选项，并在答题卡上将该项涂黑。
Barrier Islands
Texas has an extensive coastline that runs along the Gulf of Mexico. If you look closely at the map, you’ll notice that there are narrow islands located just off the coast of Texas. These are called barrier islands.
Barrier islands stretch along about 15 percent of the world’s coastlines. They are separated from the mainland by a shallow body of water. Some barrier islands spread out for more than 100 miles. In Texas, some of the largest barrier islands include Galveston Island, Mustang Island, and Padre Island.
Barrier islands are fragile (脆弱的) areas that contain an interdependent community of land, plants, and animals. All three need each other to exist. If one is harmed in some way, then the other two can suffer. For example, barrier islands are in constant danger of erosion, or loss of land, from wind, waves, and people. The steady movement of ocean waves and wind moves sand along the beaches. This movement contributes to erosion, which changes the shape and size of a barrier island over time. Plants not only provide animals with food and shelter, but it also helps keep an island’s sand and soil in place. When people pick native plants, it advances the process of erosion. This can harm the environmental balance that keeps an island’s ecosystem healthy. For this reason, visitors to barrier islands are usually warned to leave plants alone and to stay on roads and public beaches so that the land, plants, and animals are not disturbed.
As their name suggests, barrier islands provide a natural barrier that helps block the mainland from very bad weather such as strong windstorms and hurricanes. This protection saves lives, homes, and money every year. Barrier islands are also a major source of income for an area’s economy. Padre Island, for example, is visited every year by hundreds of thousands of tourists who take advantage of its sandy beaches and beautiful waters that are perfect for swimming, boating, and fishing. The dollars that tourists spend on the island help financially support the region and state.
1．Paragraph 3 is mostly about _____________.
A．what barrier islands are like    B．how barrier islands form
C．how barrier islands can exist   D．why barrier islands are important
2．Which of the following can do harm to barrier islands?
A．Keeping plants wherever they are.    B．Going wherever visitors like.
C．Fishing on public beaches.            D．Driving about on roads.
3．We can tell from the article that the author ___________.
A．lives on Padre Island and loves it
B．cares about the ecosystem on barrier islands
C．wishes less and less travelers would visit barrier islands
D．is concerned about the beautiful waters around the islands
4．Barrier islands are important because they ___________.
A．help prevent bad weather damaging mainland
B．bring in much more money than mainland
C．can protect rare plants and animals
D．provide more shelters for people