吕品

科學家们发现，波西多尼亚水生植物很有可能是地球上最大的植物，这项新发现能使公众更关注生态问题。

1 Scientists have discovered what they believe is the worlds largest plant， an underwater field of sea grass that stretches for 112 miles （180 kilometers） off the west coast of Australia. The sea grass plant is believed to be around 4，500 years old.

2 Sea grass grows together in thick fields， known as meadows. Sea grass meadows help clean the oceans water. They also provide food and shelter for many sea creatures. The climate crisis and water pollution are threatening sea grass meadows in many places around the world. But the huge sea grass meadow in Shark Bay， off the coast of Western Australia， seems to be doing very well. Its a kind of sea grass called Posidonia Australis， and it has spread widely all through Shark Bay.

3 Scientists from the University of Western Australia and Flinders University wanted to study the sea grass， so they took samples from 10 different parts of this huge meadow. Many plants create new plants by growing flowers and spreading seeds. The DNA of the plants that grow from these seeds is slightly different from the DNA of the plants that the seeds came from. By comparing the DNA from their samples， the scientists hoped to get an idea of how many different sea grass plants there were in the meadow.

4 What they learned shocked them— all of the grass samples had almost exactly the same DNA. That meant that they were all just one plant—one big sea grass plant spreading out over 77 square miles （200 square kilometers）. This makes it the largest known plant in the world by far.

5 Instead of spreading with flowers and seeds， the Shark Bay sea grass spreads by cloning itself. As its roots spread out under the sea floor， new plants shoot up from those roots. The sea grass in Shark Bay is also unusual in another way. Its a “polyploid （多倍体）”. Usually， an organism has two parents， and gets half of its DNA from each. But polyploid organisms have all of the DNA from both parents， meaning they have twice as much DNA.

Detail 1. Whats the function of sea grass meadows？

A. They can help clean the oceans water.

B. They can supply shelter for all fishes.

C. They can eat plastic to protect the sea.

D. They can provide food for any sea creatures.

Inference 2. What does the underlined word “This” in paragraph 4 refer to？

A. The same DNA. B. The spreading seed.

C. The growing flower. D. The size of the sea grass.

Gist 3. Whats the main idea of the last paragraph？

A. How the Shark Bay sea grass has grown so large.

B. What makes the Shark Bay sea grass grow so strong.

C. The sea grass has almost exactly the same DNA.

D. The sea grass is the largest known plant in the world.

Inference 4. Where is this text probably from？

A. An entertainment newspaper.

B. A guide book.

C. A nature magazine.

D. A medicine journal.

Ⅰ. Difficult sentences in the text

1. Scientists have discovered what they believe is the worlds largest plant， an underwater field of sea grass that stretches for 112 miles （180 kilometers） off the west coast of Australia. 科学家们发现了一种他们认为是世界上最大的植物，一片位于澳大利亚西海岸外绵延112英里（180千米）的海草。

【点石成金】本句中，what they believe...plant是discovered的宾语从句，an underwater field of sea grass that stretches for 112 miles （180 kilometers） off the west coast of Australia是the worlds largest plant的同位語。

2. What they learned shocked them—all of the grass samples had almost exactly the same DNA. 他们所了解到的情况震惊了他们——所有海草样本的DNA几乎完全相同。

【点石成金】这是一个主从复合句，主句的谓语动词是shocked；What they learned是主语从句，What引导主语从句并且在从句中作learned的宾语。句中，all of the grass samples had almost exactly the same DNA是对前面内容的进一步的解释说明。

Ⅱ. Text?centered chunks

provide...for 为……提供

be slightly different from 略微不同于……

spread out 散开；分散

instead of 代替；而不是

shoot up 迅速成长；迅速增加