In the time it takes you to read this sentence, the population of the Earth will have grown by 10 people. That may not sound much, but it is about 14,000 people an hour. That is the same as adding most of the population of Germany to the world every year!

    Most of these new people are born in developing countries. These countries are found in much of Africa, South America, and parts of Asia. In the developed countries of Europe and North America, the population is growing very slowly. This is because women in these countries have, on average, only one or two children. In the developing countries, many women have five or more children. In 1950, around one quarter of the world's population lived in the developed countries. By 2050, these countries will be the home to only around one tenth of the world's people.

    In the developing countries, more than one billion people already live below the poverty line (贫困线).These people don't have enough food to eat and they live in poor housing; children get little or no time at school and suffer from many kinds of diseases.

    The United Nations (UN) tries to guess population growth. At the beginning of the 21st century, the world's population was around six billion people. The UN has said that the world's population will level off at 12. 5 billion people by the year 2100. Other people think the world's population will continue to grow, reaching 14 billion people before it becomes stable or even falls.

A：Tony, is this a photo of your family?

B：{#blank#}1{#/blank#}

A：Who is this man?

B：{#blank#}2{#/blank#}

A：What does he do?

B：{#blank#}3{#/blank#}

A：Is this your mum?

B：{#blank#}4{#/blank#}

A：Where is your mum?

B：{#blank#}5{#/blank#}
 

Have you seen any scarecrows (稻草人)? In the countryside of our country, some villagers like to set up some scarecrows in the fields in order to prevent birds from harming their crops. They think that this can play a role in driving away birds. In fact, not only farmers love to use scarecrows, but also some airports have installed scarecrows in such a developed technology today, which plays a very good role in driving away birds. Some people will say that birds are not fools, and they will come back to eat after a long time. So do the birds really feel scared? Can scarecrows really play a role in driving away birds? Not very — unless you're willing to put some extra(额外)effort into them.

While traditional scarecrows who couldn't move do work against "pest birds" (eg. crows and blackbirds), the effect is almost always temporary (暂时的). Over time, the birds get used to scarecrows who couldn't move and reuse their destructive (破坏性的)habits.

However, a few tricks can up your scarecrow's game. Researchers have learned that those with realistic facial features(特征)and brightly colored clothes are better at driving away birds. Also, moving a scarecrow around every few days often helps. According to several studies, flailing(大幅波动) scarecrows get the very best results.