【推荐1】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, a harmful gas. However, scientists don’t know exactly how much seagrass 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, such as 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, trying to map the locations of the plants. 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 collected 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 believe that there is more seagrass there than anywhere else on 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 and boats to study about 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.

【推荐2】The growing population around the world does harm to the environment. More people are using more of the earth’s natural resources (资源) than ever before. Experts say poor people around the world will suffer most in the future unless environmental damage is stopped. They say more should be done to balance (平衡) human and environmental needs.

The world’s population is now over 7 billion, and it is expected to increase to about 9.3 billion by the year 2050. Since water supplies (供给) and lands are heavily used, more than 4 billion people will be living in countries that cannot meet people’s daily needs in 50 years. However, people in developed countries are using much more of the world’s resources than people in developing countries. So international laws are needed to improve poor conditions, promote (促进) social development and protect the environment. We hope that these would help improve the health and happiness of the growing population while protecting the natural world.

【推荐3】The Moon is the Earth’s satellite. It is our next-door neighbour in space.     1     Its diameter is 2,100 miles, about one fourth that of the Earth.

    2     So nothing softens the Sun’s rays. At midday the temperature on the Moon is raised by the Sun’ rays to over 100℃. At night, however, the temperature falls to—150℃.

    3     A 200 pound man weighs only 33 pounds on the Moon. When he walks, he can leap along easily.

The Moon goes around the Earth, and rotates on its axis as it revolves. It takes about 28 days to revolve, and it takes the same length of time to rotate.     4    

Every so often, the Sun, the Moon and the Earth line up in space. The Moon comes directly between the Earth and the Sun.     5     When the Moon casts a shadow on the Earth, there is an eclipse of the Sun.