When you visit the doctor, the doctor usually checks to see if your temperature is" normal". Now, new research suggests that the" normal" temperature of humans has been dropping over the last 200 years.

Human beings are warm-blooded animals. So our bodies need to work hard to stay at the same temperature.

Our bodies make heat from the food we eat. For example, we will sweat(出汗) when we 're hot or get goose bumps(鸡皮疙瘩) when we're cold.

Though the human temperature can all be a little different, most doctors consider 37C to be normal. That's been true since 1851, when a German doctor called Carl

Reinhold August Wunderlich studied 25,000 patients. His results showed an average human body temperature of 37C.

For example, a 1992 study found an average temperature of 36.8℃. In 2017, scientists looked at the temperatures of 35, 000 patients in Britain and found their temperatures were 36. 6℃ on average. Many people believed that the differences were because of mistakes in the earlier measurements.

Now a new group of researchers say," On average, the human body temperature seems to have been dropping 0.03℃ every 10 years." The obvious question is" Why?"

One of the researchers says clearly, "We don't know."

One explanation could be simply that humans have become healthier over time. Science and medicine have gotten better, and doctors have found many ways to improve the health of their patients.

The scientists also say it's possible that things like heating(供暖系统) and the air conditioning (空调) help make it.

It's important to remember that this story is about averages. But no matter what your temperature is today, it probably would have been higher if you had lived 200 years ago and that's pretty cool!

I you some questions about your schoolwork?

My mother lunch at home.

—Not really. Our bodies can _________ the cold, so sometimes we just need some water to drink.

Zhang Bo started to have great interest in meteorites (陨石) in 2009 when he saw a meteor in Hainan. So far, he (find) more than 10 meteorites.

"I (ride) a bike around Hainan Island at that time. At night, I saw a meteor streaking across the sky before it fell the South China Sea," he said.

The falling meteor lit up (点亮) not only the sky, but also Zhang's life. "I was unable  (sleep) that night. Maybe I would live a different life if I didn't see the meteor."

Soon after that, Zhang started to study meteorites. He even began to search for (they). But it was not easy sometimes could be very dangerous. Once on a visit to Altay, an area of Xinjiang, he found he couldn't open door of the house one morning. When he (final) made it to the outside, he discovered that the house had been buried (掩埋) by snow.

Zhang said when he saw the meteorites he would think of planets in our universe.

"It takes  (million) of years for meteorites to reach the earth. They bring us information about the universe and help us (well) understand it than before," he said.

—Taking plenty of exercise every day.

I think you your keys somewhere in the bedroom.