beg流利说L3-U2-4

2021年1月9日发(作者：明川)
Listening
Earth is where we all live. It is our home in the solar system. There is no other place
for us to live.
Earth isn’t just any planet. It’s a very special place. It’s special because we depend on
it for many things. Because of its importance, we need to take care of it.

We depend on the earth, for its air, its water, and many of its natural resources.
Natural resources, such as coal and oil, give us energy. Other natural resources we
depend on include forests and soil. Forests provide clean air and wood for building
houses. Soil is needed to grow plants and keep them healthy. We need to take care of
these resources and not waste them.

The Earth is a large, rotating sphere about 4.5 billion years old. The equator, which
divides the earth into two hemispheres, is about 40,000 kilometers long. The earth’s
diameter is 12,756 km (twelve thousand seven hundred and fifty six kilometers). Its
radius is half that, or 6378 km (six thousand three hundred and seventy eight
kilometers). The radius is the distance from earth’s center to its surface. Most of the
earth’s surface is covered by water. The rest of earth’s surface is land.

Just above the earth’s surface is the atmosphere. The atmosphere is a layer of gases
about 500 kilometers thick. These gases include oxygen, nitrogen and carbon dioxide.
This mixture of gases is the air that we breathe. As we move above the earth’s surface,
the air gets thinner. At high altitudes, the air is too thin to breathe. At the edge of the
atmosphere is space. There is no air at all in space.

Most of the Earth’s water is in the oceans. The two largest oceans are the Pacific and
Atlantic oceans. Unfortunately, we can’t drink ocean water. This is because ocean
water has too much salt. Fortunately, there is also water in lakes and rivers. This water
isn’t salty, so we can drink it. Only about 2 percent of the world’s water is fresh water.
Without fresh drinking water, we can’t live. A person can’t live for more than a few
days without water.

Rivers are important. Most rivers begin in mountains and end in the oceans. The water
flows from high ground to low ground. At first, rivers are small, and they’re called
streams. As water enters from other streams, a river grows.

Some rivers become very large and long. The longest river in the world is the Nile
River in Africa. It’s almost 6,500 km long (six thousand five hundred kilometers long).
As for water volume, the Amazon is the largest river. The volume of water flowing
through it per second is more than in any other river.

Another use of rivers is for energy. The energy of falling water is used to produce
electricity. This use of water supplies over 20 percent of the world’s electricity. Rivers
are also important for agriculture. Without water, farmers cannot grow food. And of
course, rivers can be used for transportation. River boats are used to carry things to
inland cities or lakes


Vocabulary
1. This man goes to running five days a week if the weather is good. On the weekends
he runs 10 kilometers unless the weather is bad.
2. This woman really enjoys reading, especially works of fiction. She has read
hundreds of books.
3. This young couple enjoys watching old movies such as Titanic. They both cried
when it sank and many people went down with the ship.
4. These young boys enjoy playing sports on the weekend. Sometimes they play
basketball and sometimes they play football.
5. This young man eats too many sweets so he is overweight. He needs to eat fewer
sweets and exercise more.