2 . From goldfish to sharks, fish of all sizes have lived on Earth for hundreds of millions of years. But do they ever get thirsty?

The answer is yes! Some fish do, at least. But there is a big difference between fish that live in saltwater and ones that live in freshwater.

Bony fish have some salt concentration（含盐量）in their bodies. For bony fish in saltwater, their concentration is lower than the water they live in. Through osmosis（渗透作用）these fish will lose lots of water through their bodies. In order to make up for this loss, they drink lots of water, so it’s easy to say that they can be thirsty. Although drinking saltwater is never a good idea for humans, fish can drink it because they can get rid of the salt through their gills（鳃）.

But sharks are an exception. Sharks can make their salt concentration match the water around them. They do this by building up urea（尿素）in their blood, so they probably don’t get very thirsty. But blood with a high salt concentration can also be bad. The high concentration means sharks won’t do very well in freshwater—water can enter the sharks’ bodies by osmosis and even cause them to explode!

Freshwater fish, on the other hand, are unlikely to become thirsty. Because they live in a less salty environment, they have a different problem: water goes inwards and dilutes（冲淡）their blood. Freshwater fish therefore need to get rid of this extra water. So now we know that saltwater fish can become thirsty and drink water, while freshwater fish will avoid drinking but pee（小便）a lot.

3 . Fifteen volunteers have come out a difficult situation from a cave (洞穴) in the southwest of France after spending 40 days without clocks, phones, or sunlight for a human isolation experiment. The group had no communication with the outside world and was not able to use any electronic devices.

Eight men and seven women were grouped to live in the cave as part of a $ 1.4 million project called Deep Time, which set out to explore the limits of human ability to gradually change their behaviour and attitudes in the new situation. The experiment ended after 40 days.

During their time in the cave, the volunteers slept in tents and made their own electricity with a bike since there was no natural light. They also got water from a well (井) 146 feet below the earth. Since there was no sunlight, the team had to follow their biological clocks to know when to sleep, eat, or do daily tasks. To no one’s surprise, they quickly lost their sense of time.

One of the volunteers said he thought he had been underground for 23 days. Another volunteer said he ran 10-kilometer circles in the cave to stay fit. And he couldn’t wait to leave the cave. But other volunteers felt differently, with two-thirds saying they wanted to stay in the cave for longer. Some even thought it was as if they could press pause and stop to live.

During their time in the cave, scientists carefully watched and checked the volunteers including their sleeping patterns, social activities and cognitive functions (认知功能). The experiment will help scientists understand how human brains can help people adapt (适应) to serious living conditions in new situations.

7 . Water is important for our body and health. It is important because almost all parts of the human body have water. And about 60%-70% of our body is made from water. ①If there is no enough water, our body _________ work properly. ②We can get it through several ways, such as having fruit, vegetables, tea and milk. How much water do we need every day? It is different every day. It depends on our daily activities and the temperature of the day. Generally speaking, an adult needs about eight cups of water every day. ③But when we do some exercise or when the temperature is high, __________.

8 . Each year, hundreds of people climb Mount Qomolangma. Most of them do it to achieve a personal dream. But for some, they push themselves up the mountain for other purposes.

On September 24, 2021, Guo Yongjie and the other seven members of a team set out at a height of 5,800 meters. They reached a height of around 6, 200 meters several hours later. This was the second time the Chinese team had climbed Mount Qomolangma in 2021, following their first trip in August.

“Desideria himalayensis,” Guo cried as soon as he saw a plant. He took pictures of the plant from all directions and recorded its height and location right away. It was the first plant they found at a height above 6,000 meters. What made Guo more excited was that some of the siliques (角果) of the plant had divided, which meant the team had a chance to collect its seeds (种子).

To do research, a complete seed sample (样本) needs at least 2,500 seeds. However, since seeds are scarce at high points of Mount Qomolangma, it is hard to collect 2,500 seeds. So the team could only try to collect as many as possible.

In July 2022, after being kept in very low temperatures for nearly a year, the seeds collected on Mount Qomolangina were taken out to test if they were alive. And soon all the seeds germinated (发芽). It means that China has successfully collected and kept those valuable seeds.

A seed carries the hope of life from the moment it comes into being. For China, those seeds have brought more hope to its plant protection.

9 . Blood transfusions（输血）have become a real life saver in modern medicine. But not so long ago, blood transfusions were dangerous and killed as many people as they saved. That is, until 1901, when an Austrian scientist discovered that humans do not all have the same blood type. His research showed that humans, in fact, have one of four blood types A, B, AB and O.

Before the discovery of the four blood types, it was believed that you could give the blood of any person to any other person. Giving a person the wrong type of blood often leads to death because the two different blood types fight each other. When giving a blood transfusion, doctors need to know the blood types of the donor（输血者）and the recipient（受血者）.

No matter where you live on this planet, your blood will fall into one of the four types. Some blood types are rarer than others. In European cultures, the most common blood type is O. Among Asian populations, the B blood type is common, while it is very rare in European populations.

People with type O blood are “universal（万能的）donors”. Their blood can be given safely to people from any of the other three groups. People with type AB blood are “universal recipients”. They can receive blood from any of the other three groups.