Monarch butterflies from eastern Canada make the most amazing journey in the insect world. Each year, this butterfly travels about 3,000 miles to its winter home in central Mexico. How can it fly so far? And why does it make this long and dangerous trip? Scientists still don’t have an answer.

For many years, people in Mexico wondered where the orange-and-black butterflies came from every winter. Then, in 1937, a scientist started to follow and study the butterflies. For the next 20 years, he discovered that one butterfly started its trip in Canada. Four months later, it arrived in Mexico.

The length (长度) of the butterflies’ trip is only one part of the mystery. Another amazing thing is that the butterflies always return to the same area in central Mexico. How do the butterflies find their way back to the same place? This is an interesting question because only every fourth generation (代) makes the trip south. In other words, the butterfly that travels to Mexico this year is the great-great-grandchild of the butterfly that traveled there last year.

Each year, four generations of a Monarch butterfly family are born. Each generation of the family has a very different life. The first generation is born in the south in late April. It slowly moves north, reproduces (繁衍) , and then dies. On the trip north, two more generations are born, reproduce, and die. Each of these generations of butterflies lives for only two to five weeks. In the autumn, the fourth generation of butterflies is born. This generation has a much longer life. It lives for about eight months. This generation of butterflies makes the amazing journey back to the winter home of its great-great-grandparents. The butterflies spend the winter there, and in spring they reproduce and then die. Theiroffspringwill be the first generation of the next circle of life.

Today, people are still studying Monarch butterflies. But they are not clear about everything. There are still many mysteries to be solved.

I’m a Monarch butterfly. You’ll see me in①______in the winter. No one has taught me the route, but I can find my way to the②______place where my ancestors travelled. As the③______generation, I can live for eight months. For scientists, I’m a④______to be solved.

Do you have a pet? Owning a pet is becoming very common(常见的) in China these days. And pet owners are now willing to spend more money on their pets than before.

According to a report from Goumin.com and Pet Fair Asia, Chinese people living in cities spent a total of 202.4 billion yuan on their pets in 2019. Most pet owners are people born after 1990. Most of them have high incomes and are well educated. Pet owners in China are spending more on pet food, clothing and furniture, according to report from Euro monitor International.

Miss Hou, 28, lives in the city of Chengdu. She spent 6,000 yuan on her two cats last year. I bought tinned cat food from the United States, New Zealand, Japan and Thailand, Hou said to Xinhua. If I have time, I also cook for them, she said.

An aging society and fewer people having children are among the main reasons for keeping pets, said Liu Xiaoxia, CEO of Goumin.com. Keeping pets has met the emotional(感情的) needs of many people. Almost 60 percent of pet owners see their animal friends as their own children, Liu said.

Beating loneliness might be another reason. Many young people are leaving their hometowns to make a living in big cities. They are suffering(忍受) from great loneliness and pressure, as they have few friends and face a high cost of living. Keeping pets will help them feel relaxed, the 2019 Chinese Pet Industry White Paper said.

Kangaroos live in Australia.They can’t run and they can’t walk. But they can jump more than nine meters at a time. They can jump very fast — thirty kilometers an hour. Baby kangaroos are very small — only 3 cm long. They can’t jump and they can’t see. A young kangaroo is always in its mother’s pouch for the first six months. They can see when they’re nine weeks old. They can jump when they’re eight months old.

The biggest animal on the earth is the blue whale. It weighs about 80 tons — more than 24 elephants. It’s more than 30 meters long. A new born baby whale weighs the same as a big elephant.

A cat won’t die when it falls from a very high place. This is because it can turn itself up the right way to keep its body safe. One cat fell from the 32nd floor onto the street, but was just hurt a little.