Americans were shocked to discover that the national bird was in danger of disappearing from the skies forever. Studies in 1970 showed only about 1,000, or fewer, bald eagles(秃鹰) in the country.

    The major cause of the problem was people. The spread of civilization(文明) destroyed many of the eagles' feeding and nesting areas. And the eagles were being affected by D-D-T and other insect poisons. The poisons were in the animals the eagles ate. They reduced the eagles' ability(能力) to use calcium(钙). This made the outside of the eagles' eggs very thin. Often, the eggs broke before baby birds were developed.

    In 1972, the U. S. government banned(禁止) D-D-T. People also became interested in protecting places where eagles live. And stronger efforts were made to carry out laws protecting the birds. Scientists began a program that placed baby bald eagles which were born under human care, into nests of wild bald eagles. Often, the wild birds accepted the babies.

    These efforts appear to have been successful in saving the American bald eagles. Today the number of the bald eagles has increased to more than 11, 000.

Dear Simon,

Thanks for telling me about your problems!

I do hope all the advice can be helpful to you.

Yours,

Joy

Have you ever unlocked a Hello Bike? Have you ever used Meituan to order a meal? Have you ever enjoyed watching the short-form videos on Douyin? Well, if no one had invented the cell phone, none of these would have been possible.

Luckily, someone did invent the cell phone. That person is Martin Cooper, and he did that 51 years ago, in 1973.

Cooper used to work for Motorola. In the 1970s, the company was competing with AT&T, a larger company, to make a cell phone system. Cooper didn't think Motorola's product was good enough. He didn't like AT&T's idea of a car phone, either. The man wanted to give the world something new. He wanted to make it possible for people to talk on their phones anywhere.

It took Cooper and his team 90 days to design (设计) the world's first cell phone. The product was called DynaTAC. People could talk on it for 25 minutes before its battery (电池) died. The phone's short battery life wasn't a big problem, Cooper once joked. Why? Well, the phone was too heavy (1, 100 grams) to hold in hand for too long!

On April 3, 1973, Cooper made the world's first public cell phone call. He called Joel Engel, an AT&T manager. Cooper told Engel, "I'm calling you on a cell phone. It's a real, handheld cell phone." On the other end of the line, there was only silence.

Cell phones have changed a lot since that first call. They're much smaller and can do many more things. Cooper, now 96, is surprised at the progress. But the man has also kept thinking about life in the future. "I must keep learning all my life," he says. "Or I'll lose the ability to learn-that would be terrible!"

Betty has a new jacket. She likes it because there are different letters(有不同的字母) on it and they are in different colors.

The first letter is D. It's blue — the color of the sky(天空). The letter R is yellow. It's a beautiful color — the color of the sunflower(向日葵). The letter E is red. It's the color of the apple. The letter A is purple(紫色的). It's Betty's favorite color. Look! Her cap is purple, too! What color is the letter M? It's green. Betty's sister, Rita, likes the color best.

The new jacket is very beautiful. Betty likes to wear it to school.