In Australia, National Tree Day is on the last Sunday in July. In China, Tree Planting Day is on 12th March. Trees are very important in our life. Trees make our city beautiful. We can get a lot of things from trees. We get fruit from trees. We also get wood from trees. We use wood to make pencils, desks and chairs. We can use wood to make paper, too. Trees can keep the air clean. They can cool the air, too. So we should love trees. Wе should plant more trees.

Mobile phones are one of the most useful inventions of the last 50 years, but not everything that is said about them is good. Mobiles are often believed to be the cause of a number of things from poor eyesight and headaches to house fires. There’s even one theory that mobile phones should be responsible for the disappearance of bees!

The theory is that the radiation (辐射) given off by mobile phones does great harm to bees’ navigation systems (导航系统). Bees have built-in system a bit like GPS and this helps them find their way back to their hives. But recently, thousands of bees have failed to find their way home. It is believed they are dying far from their hives.

The problem was first noticed by beekeepers in America and is a lot more serious than it at first seems. The important thing about bees is that most of the crops in many countries of the world are pollinated by them. Without bees, the crops can’t continue to grow. Many beekeepers in Europe have reported losing between 50 and 70 percent of their bees. Jim Piper, London beekeeper, said to the reporter, “My business is becoming worse. Twenty-nine of my forty hives are now empty.”

Nobody knows for sure whether the theory is true or not, but it’s a fact that bees are disappearing in very large numbers. And we can’t manage without them. Einstein said that if all our bees disappeared, man would only live for four more years! If the mobile phone theory is correct, we need to do something about it right now—before it’s too late.

Sasha Winkler is a graduate student at the University of California, Los Angeles(UCLA). Winkler works with small monkeys. These monkeys would play together by running after each other. One day, Winkler noticed a sound the animals made during the play. 【小题1】 But it reminded Winkler of quiet laughter. This made Winkler wonder if other animals did so while they were playing too.

Then, Winkler worked with Greg Bryant, a professor at UCLA. Winkler and Bryant read and reviewed research written by other scientists who study animals. They identified(确认) 65 different animals which laugh while playing. 【小题2】

Winkler and Bryant found that many animals laugh so that their play partner knows they are having fun. 【小题3】 Laughing is a way for animals to prevent play from becoming dangerous or harmful. Some animals also make a “play face”, giving an expression like a smile to show that they are happy.

But animal laughs are not quite the same as human laughs. 【小题4】 When monkeys play, they make a purring(低鸣) sound. Rats make a very high-pitched trill(高音颤音) sound. Dolphins whistle while they swim and jump together.

Two types of birds also made laughing sounds: the Australian magpie(喜鹊) and the kea(食肉) parrot. In fact, laughter is one way that kea parrots let others know it’s time to play. 【小题5】

Most animals that laugh and play are mammals(哺乳动物) like us. Animals like fish, frogs, snakes don’t seem to laugh, and scientists don’t know if these animals even play at all.