A crow(乌鸦) is about twenty inches (英寸) long and black all over. Crows are dirty birds because they live on bad food. Crows eat a lot of waste food. In this way they are more useful to us than any birds. They clean up the dirty things in our streets. Crows are always hungry. They look for food all day, and in the evening you can see them in large numbers flying back to their nests(巢) in the trees. They sleep there at night.

    Crows are much noisier than other birds. Very often a large number of crows will get together on one house and talk. Sometimes they talk together, and sometimes they do it by turns(轮流) like human beings(人类). It is easy to tell(判断) from crow's sound if they are pleased or angry. Perhaps crows talk a lot because they are friendly birds. A pair of crows will live together all their lives, and if one of them dies, the other one becomes very sad and quiet for the rest of its life and some time later it dies too.

     What is a hurricane?

    You may already know that hurricanes are storms that can cause devastating(毁灭性的)waves, wind, and rain. They happen during “Hurricane Season,” which is from June 1st until November 30th in the Atlantic Ocean and from May 15th until November 30th in the Pacific Ocean.

Categories(类别)of Hurricanes

    There are five categories of hurricanes, which are based on wind speeds. The categories help people know how much damage(危害)a hurricane may cause because the greater the wind speed, the more dangerous the storm is. For example, a Category 5 hurricane has winds over 155 miles per hour, which are strong enough to destroy the buildings along the shorelines completely.

Hurricane Dangers

When a hurricane happens together with heavy rainfall, there can be a devastating flood. The centre of a hurricane is called the eye. While most of a hurricane has dangerously strong winds, the eye is actually(事实上)a calm area in the storm. When the eye of a hurricane passes over land, people might think that it's over, but before long the wind and rain increase again as the second part of the hurricane moves through.

Hurricane Safety Tips

    There is no way to stop a hurricane or make it change direction, so if you ever find yourself in the path of a hurricane, be sure to remember the following safety tips.

    Be sure you have a radio, batteries, fresh drinking water, and enough food.

    Tell neighbours, friends, and family members your emergency plans. Tell them where you'll go if you need to leave your home.

    If you live near the ocean, leave your home and travel to a safe place. You could stay with a friend or a family member, in a hotel or in an emergency shelter area.

    Stay inside during the storm. You could be seriously injured (受伤) if you go outside.

How does a young dog or cat get to know a new home? The animal uses its nose. Right away it smells its new places. Then it makes wider and wider circles, smelling all the time. Before long it can find its way home very well, even in the dark. It simply follows something it knows well.

    Stories happen about animals who found their way across land they had never smelled before. Take the case of Smoky, a small white cat. Smoky had some funny red hair around its right ear. One day Smoky and his owner began a long journey. They were moving from Oklahoma to Tennessee. When they were just eighteen miles from their Oklahoma home, Smoky jumped out of the car. Then he found his way back to the old house. There he wandered around outside for many days. Finally he disappeared.

    A year later Smoky meowed at the door of a house in Tennessee. A man opened the door. "Is that you, Smoky?" he said in surprise. At first he couldn't believe it. Then he saw the red hair around its right ear. It was Smoky!

    Scientists have been experimenting with four-leg robots for years. They want to use robots to carry heavy things over difficult land.

    But providing enough power for those kinds of robots has been a problem. Now, that has changed. Engineers at MIT have designed a running robot that runs on batteries. Scientists say their robots will soon be able to run like cheetahs, the fastest land animals on Earth.

    One difficulty in designing these types of robots continues to be providing power. These machines are still quite heavy and they need a lot of power to run. But the cheetah-like robot designed by engineers at MIT is light enough m run on batteries. The robot weighs just 30 kilograms. The robot needs only about 700 watts of power to run. This robot can actually jump 40cm high and it can land very safely and then it can run. The robots limbs and other parts were made in a three-dimensional or 3D printer. A strong, light-weight material called Kevlar is used to make the robot's part stronger.

    But the development of MITs robot is not without its own set of problems. The robot's limbs must support heavy force, and sometimes they break.

    Scientists say the new technologies used on this robot may be used in the making of limbs for disabled persons and other machines. Some of those machines may help save humans from performing difficult and dangerous jobs.