2 . Feeling overwhelmed by your to-do list can certainly make you unhappy, but new research suggests that more free time might not be the magic medicine many of us dream it could be.

In a new study, researchers found that people with more free time generally had higher levels of subjective well-being, but only up to a point.

People who had up to two hours of free time a day generally reported they felt better than those who’d had less time. But people who had five or more hours of free time a day generally said they felt worse. So ultimately the free-time “sweet spot” might be two to three hours per day, the findings suggest.

Part of finding the “sweet spot” has to do with how people spend the extra time they have. The researchers conducted several smaller online experiments. In one they asked participants to imagine having 3½ to seven free hours per day. They were asked to imagine spending that time doing “productive” things (like exercising) or to imagine doing “unproductive” activities (like watching TV). Study participants believed their well-being would suffer if they had a lot of free time during the day, but only if they used it unproductively. In other words, how people use their free time matters.

Of course, what feels “productive” is up to you. If watching two hours of Real Housewives in your free time increases your happiness, you should do that. And even more traditionally productive or purposeful activities can be easy and fun. Engaging in a bit of low-key cardio, like walking, can help burn stress. Free-time activities like reading, cooking or gaming are also known to put people in a state of flow.

In cases when people do find themselves with huge amounts of free time, such as retirement or having left a job,” Sharif said, “our results suggest these individuals would benefit from spending their newfound time with purpose.”

3 . A common claim states that a sheet of paper cannot be folded in half more than seven times. But is this true?

In 2002, Britney Gallivan, then a junior in high school in Pomona, California, folded a single piece of paper in half 12 times. She currently holds the Guinness World Record for the most times to fold a sheet of paper in half.

The prompt that led Gallivan to accomplish these feats was an extra-credit challenge in math class to fold anything in half 12 times. Her teacher asked the students to fold something thicker: a piece of paper.

Gallivan said “it was very frustrating, as I had many unsuccessful attempts at trying to fold different papers in half. I began to question if folding paper in half more than eight times could be impossible.” However, Gallivan recalled. “I knew I needed to understand what was limiting the folding progression.”

The equations that Gallivan came up with calculated how many times a sheet of paper could be folded. She found that in order to fold many times, a long thin sheet is needed — the more a sheet is folded, the thicker the resulting stack becomes, and once the stack becomes thicker than it is long, there is nothing left to fold. She ultimately set her record with a sheet of tissue paper she found online that was 4,000 feet (1,219 meters) — more than three-quarters of a mile, or over a kilometer — long, Guinness World Records noted.

“Working on the problem took a tremendous amount of time and effort,” Gallivan said. “As frustrating as it was at times, I learned an immense amount from the experience, which has been valuable to me throughout my life in more capacities than one would expect.”     

Since Gallivan set her record, others have made claims of folding a sheet of paper more than 12 times. Still, “I anticipate that my current record will be surpassed,” Gallivan said.

There was a state     1     (call) Zhou (周) in the Chinese history. One day, the king of Zhou asked his officials for advice on     2     (deal) with prisoners of war. An official said, “If you love someone, you     3     (suppose) to love even the crows on the roof of his house. The prisoners of war are enemies fighting     4     us. In my opinion, we’d better kill them all.”

But the king didn’t agree with him. “I think we should treat the prisoners of war     5     (different) by differing them into those     6     are guilty or not. The guilty ones will be sentenced to death in order to avoid future disasters.”

Then another one said, “Your majesty, I think all the prisoners should be set free and sent back home to work in the fields and support     7     (them) by their own labor.     8     , you should keep strictly the rules for reward and     9     (punish). The people are sure to believe in you if you govern our country by morals and laws.”

The king thought the official’s proposal was quite reasonable so he accepted and followed it. As a result,     10     domestic situation soon settled down and gradually the country became stronger.

7 . For centuries, the power of Chinese emperors rose and fell with their control of the Grand Canal. Today, this waterway is shorter than it once was, but it is still the longest man-made river in the world. Importantly, the Grand Canal continues to provide a significant cultural and economic link for modern China.

The   original   canal   system   began around the year 605. China’s Emperor Yang realized that he needed a better way to move food quickly to his army from China’s southern rice-growing region to the country’s north. So about one million people-mostly farmers-worked on the construction of the first section of the Grand Canal, which took six years.

Over the next 500 years, the canal’s importance grew. However, by 1127 , parts had begun to deteriorate. In 1279, Kublai Khan began to repair and build new parts of the canal, which created a more direct north-south route to and from Beijing. Future rulers continued to expand and improve the waterway, and it eventually became an important national lifeline.

In addition to moving rice around China, the Grand Canal was an important cultural connection. Soldiers, businessmen,and artists transported ideas, regional foods, and cultural practices from one part of China to another. According to ancient stories, this is how Beijing acquired two of its best-known trademarks. Peking duck,a dish from Shandong Province, and the Peking opera, from Anhui and Hubei regions,were both brought north by the canal.

For more than a thousand years, goods have been transported along the Grand Canal.Even today, the country’s watery highway plays an important economic role in China. Boats continue to carry tons of goods. In addition, local governments-eager to in-crease tourism and real estate (房地产) development-are beautifying areas along the canal.

In 2005, a group of citizens proposed that the historic Grand Canal be made a UNESCO World Heritage Site. It was officially granted (批准) in 2014. The hope now is that the Grand Canal-one of the world’s great engineering achievements -will continue to link north and south China for centuries to come.

9 . Putting more green space around a school may help students develop some mental abilities, a study suggests. Researchers tested students repeatedly over the course of a year on attentiveness (专注力)and working memory, which is the ability to keep something in mind temporarily for performing a task. On the whole, students whose schools were surrounded by more green space improved more than pupils from schools with less green space.

The study tracked more than 2,000 students in 36 primary schools in Barcelona, Spain. The pupils were in the second to fourth grades when the study began. Green space may help mental development by reducing air pollution from vehicles, according to an article by the researchers that included pollution data from the schools. It may also help by reducing noise and encouraging physical activity, researchers said.

Policy makers should know that “more green around the school is better for cognitive development and that they should make sure that kids can see and play in green areas,” one author Mark Nieuwenhuijsen said. “Existing urban schools should think about replacing concrete or other hard surfaces with green space,” he suggested, “and even a few trees may help.”

The researchers used satellite images to group schools according to how much green space appeared on the school grounds and within about 55 yards of the school property. Their analysis showed that differences in socio-economic factors between schools did not account for the study outcome.

Sally Augustin, a psychologist, said the results made sense to her. She said the results fit with previous findings that views of nature help children and adults lower stress and perform mental tasks better.