Humans can see different colors. But scientists     1     that most animals cannot see colors. The world is black and white to them.

Scientists did an experiment. They gave dogs food every time they     2     a certain piece of music. The dogs got ready to eat only when they heard this piece of music. They did not get ready to eat when they heard other pieces of music.

Then the scientists gave the dogs food every time they showed them a certain color. The dogs got ready to eat when they saw this color. Then the dogs     3     another color, and they also got ready to eat. The colors were all the same to them.

Colors are not all the same to monkeys, however. For example, if we put food in the red box, and do this every day, a monkey will always go to the red box     4     food. If we then put food in a blue box, the monkey     5     to it.

In many countries, pets are well     1    . In the United States, 95 percent of pet owners think of their animals as family members. About half buy them birthday gifts. And it’s a two-way street（双向沟通的方式）. People who have pets     2     have lower blood pressure（血压）. They are also less likely to suffer from heart problem.

Scientists are finding more and more proof (证据) that animals can also help     3     mental（精神上的）health. Some clinics have been using “pet therapy（疗法）” alongside(与…同时)     4     medicine. Here is a look at some of the most effective treatments(最有效的治疗）.

Rabbits

In one study, scientists told a group of stressed-out adults to pat a rabbit and a rabbit toy. The toy had no use. Touching the living rabbit, however, made their stresses     5    .

Crickets(蟋蟀)

Animals don’t have to be soft and lovely to help. In a 2016 study, elderly people who     6     given five crickets in a cage reported feeling happier after eight weeks. The act of caring for an animal seemed to make the     7    .

Horses

Horses are among the most-studied therapy animals. In Europe, they have been involved （卷入）in medical treatments（治疗） since the 1860s.     8     like brushing the fur(毛皮) of a horse have been shown to reduce stress in people of all ages.

Fish

One study focused on people who had Alzheimer’s disease（阿尔茨海默氏病）. When they ate food in front of a tank（缸） of colorful fish, they ate more.

Dogs

Some children have difficulty     9     to read. However, they often feel less worried when reading aloud to a trained dog. Over time,    10     attitudes change and skills improve.

Learning a new language is hard. In a     1     research, scientists found that your chances of reaching fluency (流利) in a new language drop off at the age of 10. Does that mean you should give up your French class     2     you are older than 10? No!

The research found that it’s “nearly     3    ” to reach fluency if you start learning a language after age 10. That’s not because your language     4     start to get worse. “You’re still learning     5    ,” says Joshua. “It’s just because your     6     to learn starts dropping at around 10 or 11 years old.”

The researchers say people who try to learn a new language after age 10 may still become     7     good. But they will probably not become fluent. Kids may be better than adults     8     learning new languages for many reasons. One is that children’s brains are more adaptable (能适应的) than adults’ brains. This     9     they are better able to change. Kids may also would like     10     new things. And adults may depend on the rules of their first language. But kids are able to     11     a new language without them.

Wuyi Rock Tea is a kind of oolong tea. The tea trees grow in rock cracks (裂缝) of Mount Wuyi. That’s     1     it’s called Wuyi Rock Tea.

Wuyi Rock Tea is famous     2     its different smell. The best kind of it is Dahongpao.

With     3     long history, Wuyi Rock Tea dates back to (追溯到) the Shang Dynasty. In 2006, the skills (技能) of     4     Wuyi Rock Tea were added (添加) to China’s national intangible cultural heritage list (国家级非物质文化遗产名录). In March 2021, President Xi Jinping     5     a tea garden in Wuyi Mountain.

Zhang Huichun, 65, is a master (专家) of making Wuyi Rock Tea. In 1980, he learnt to make the tea and opened a tea factory. It took him 10 years to     6     the skills.

There are 13 steps (步骤) to make it. Drying, shaking and roasting (烘)     7     three of them. Although Zhang is already good at it, he is still learning. “Every step is full of     8     because of different tea trees and weather. Every time is an adventure (冒险).”

To help more tea makers, Zhang often     9     with schools to teach the skills. “It’s     10     responsibility (责任) to pass on the skills,” he said.