F
Seagrass, an underwater plant that grows on the ocean floor, is very important for sea life. It also helps prevent global warming by storing carbon dioxide, a kind of gas. However, scientists don't know exactly how much seagrass there is at the bottom of the ocean. With the help of tiger sharks, a team of researchers has discovered the world's largest seagrass meadow (grassland) on the seafloor near the Bahamas.
Seagrass meadows are home to many different kinds of fish, shellfish, and so on. Large sea animals like sharks, also spend a lot of time there looking for food. Seagrass can grow in very deep and dark waters, making it difficult to find. But sharks can dive deep into the water and get to the areas people cannot reach.
After noticing tiger sharks swimming through seagrass off the Bahamas, an American scientist worked with a seagrass expert(专家), trying to map the locations of the plant. The researchers fitted seven tiger sharks with cameras. Since tiger sharks swim in groups, they placed satellite tracking tags(卫星跟踪器) on eight other sharks to find out exactly where the animals swam. They gathered hours of videos of the tiger sharks swimming through seagrass.
The researchers found more seagrass growing near the Bahamas than they expected—in fact, they believed that there was more seagrass there than anywhere else on the earth. The new finding increased the total number of seagrass known to exist by 41%. However, more research is needed to discover the true size of the seagrass meadow.
Scientists often depend on findings from divers(潜水员) and boats to study the underwater world, but this team found that working with animals improved their understanding. They are now placing cameras on sea turtles to study seagrass in the Red Sea. Hopefully, more mysteries about seagrass will be solved.
()1.Why is seagrass difficult to find under the water?
A. Because seagrass is too small to be seen.
B. Because it grows in very deep and dark areas.
C. Because it's difficult to reach the bottom of the sea.
D. Because tiger sharks almost eat it all up.
()2.What is Paragraph 3 mainly about?
A. The reason for the research.
B. The method to do the research.
C. The discovery of the research.
D. The scientists of the research.
()3.How will scientists work out the mysteries about seagrass?
A. By hiring more divers and boats.
B. By using better cameras.
C. By having discussions with seagrass experts.
D. By working with animals.
()4.The article is written to .
A. show a special project on global warming
B. describe the features of sea animals
C. share a new way of doing undersea research
D. tell the importance of seagrass

1. B 【点拨】根据“Seagrass can grow in very deep and dark waters, making it difficult to find.”可知，海草可以生长在非常深和黑暗的水域，很难被找到。故选 B。
2. B 【点拨】根据第三段内容可知，本段主要讲了研究方法。故选 B。
3. D 【点拨】根据“Scientists often depend on findings from divers(潜水员) and boats to study the underwater world, but this team found that working with animals improved their understanding.”可知，科学家通过和动物合作来解开海草之谜。故选 D。
4. C 【点拨】通读全文可知，本文主要介绍了海草的重要性以及科学家如何利用虎鲨进行海底研究，即分享了一种新的海底研究方法。故选 C。