阅读理解

B

    Animals grow up in different ways. Some newborn animals are helpless but their mothers protect them. A newborn kangaroo is very small. It is only a few centimeters(cm) long. It closes its eyes and doesn't have hair. It stays safe in its mother' s pouch(育儿袋) for a long time.A newborn monkey can not walk. Its mother carries it everywhere.

Other baby animals can walk soon after they're born. They learn to run with their mothers when danger is near. A baby zebra can run, an hour after it is born.

    Some baby animals are born in a place that is safe. Baby wolves are usually born in big holes with little light. Other baby animals are born in the open. A baby elephant is often born on open land.

    Animals that drink their mothers' milk are called mammals. A mother bear's milk is rich. Baby bears have milk for a few months. This is the same with baby zebras. As baby animals grow, they need solid(固体) food. Baby lions eat what their mother can catch!

    How long is a year? Most people say a year is 365 days. It takes about 365 days for the earth to go around the sun. In fact, it takes a little longer for the earth to go around the sun. It needs 365 days, 5 hours, 48 minutes, and 46 seconds.

    If a year has only 365 days, what happens to the extra(额外的) 5 hours, 48 minutes, and 46 seconds? The answer is this: Every four years, we have another day. It's February 29, and we call this day " a leap day(闰日)".This kind of year is called "a leap year". A leap year has 366 days.

People born on February 29 are called leap-day babies, or leapers. There are about four million leapers in the world. When do they celebrate their birthday? Do they celebrate only once every four years? Some leapers celebrate the birthday on February 28, and others celebrate it on March 1. Think about it: A twelve-year-old leaper may have celebrated only three birthdays on the real day after he or she was born!

    Which year are leap years? Years that can be divided(除尽)by four are leap years. The year 2000 was a leap year. Then 2004,2008,2012,2016 were the next leap years. If you know a leaper, you must say "Happy birthday!" to him or her on the leap day, because you just have one time to do that every four years!

    When you watch TV and play video games you make global warming(全球变暖) worse! To make electricity, fossil fuels(矿物燃料) are burned in big factories. But burning fossil fuels also makes greenhouse gases. This means that every time you use electricity you help make global warming worse!

    Cars are also making global warming worse. They burn fossil fuels in their engines, and send lots of greenhouse gases into the air.

    So what can we do to stop global warming?

    Try to use less electricity. First, turn off lights, your television, and your computer when you stop using them，You could also try to watch less TV. But you may find it hard to do these! Second, plant trees. Not only is it a fun thing to do, but it is also a great way to lower the number of greenhouse gases in the air. Trees take carbon dioxide(二氧化碳) out of the air when they grow. Last, don't throw away your rubbish, but try to recycle it. Because if rubbish is not recycled, it rots(腐烂) and makes a greenhouse gas called methane(甲烷). So try to recycle cans, bottles, plastic bags and newspapers. It'll make you feel great! And it'll help the Earth.

    Have you ever paid attention to the Air Quality Index (空气质量指标) or AQI reported in the newspaper? The AQI helps us understand what the air quality around us means to our health. The AQI uses colors, numbers and words to tell us about the air. Let's see what these colors and numbers mean.