5 . Relatives of starfish, brittle stars (海蛇尾) spend most of their time hiding under rocks in the ocean or digging in the sand. These shy marine creatures have no brain to speak of—just nerve cords running down each of their five wiggly arms, which join to form a nerve ring near their mouth.

“There’s no processing center. Each of the nerve cords can act independently. Instead of a boss, it’s like a committee. That seems to be enough to learn by association,” said lead author Julia Notar. This type of leaning involves associating different stimuli via a process called classical conditioning (条件反射).

Classical conditioning has been demonstrated in a handful of previous studies in starfish. But brittle stars and similarly brainless starfish have not been tested.

To find out if brittle stars have the ability of learning, the researchers put 16 black brittle stars in individual water tanks and used a video camera to record their behavior. Half the brittle stars were trained by dimming the lights for 30 minutes whenever the animals were fed. Every time the lights went out, the researchers would put a bit of shrimp in the tanks, placed just out of reach. The other half got just as much shrimp and also experienced a 30-minute dark period, but never at the same time—the animals were fed under lit conditions.

Whether it was light or dark, the animals spent most of their time hiding behind the filters in their tanks, only coming out at mealtime. But only the trained brittle stars learned to associate darkness with food. They didn’t need to smell or taste the shrimp to react.

Notar said the results are exciting because classical conditioning hasn’t really been shown definitively in this group of animals before. “Knowing that brittle stars can learn means they’re not just robotic scavengers (清道夫) cleaning up the ocean floor,” Notar said. “They’re potentially able to expect and avoid predators (捕食者) or expect food because they’re learning about their environment.”

6 . Pat Patterson, a pilot for 25 years, had never met anyone like the handsome young man in the wheelchair who faced him at the Medford, Oregon, airport on July 28, 1976. Mike Henderson, a quadriplegic (四肢瘫痪者), wanted flying lessons.

As a 22­-year-­old Coast Guardsman eight years before, Henderson had fallen off a dock and landed on a floating log, breaking two of his bones. Doctors said that he would probably never walk again, let alone fly. “Here was this doctor telling me how it was going to be,” he says, “but no one was going to limit my freedom to try.”

Henderson parked his wheelchair next to the airplane and began to climb up onto the wing. He injured his elbow on the way, and after a great struggle, finally managed to pull himself into the airplane’s pilot’s seat. In the flight office, Pat Patterson watched in disbelief. “He crawled his way up that wing!” he says. “It took him 45 minutes. When I went out, he was sitting in the pilot’s seat, bleeding from his injured elbow all over the place. When I saw him go through that much pain, I knew nothing could stop him.”

Now everything was up to the instructor and the student, and together they set about solving each problem as it arose. A small piece of carpet gave Henderson traction (摩擦力) to climb the slippery wing. A headset freed his hands from the radio microphone, and the two men developed a moving bar that enabled Henderson to operate the airplane more easily.

Three weeks and eight flying hours after the first lesson, Henderson and Patterson happily phoned Dr. Stoddard — Henderson’s physician. At the airport, as the physician looked on, Henderson quickly wheeled himself around the airplane, doing a thorough, professional ground check. With Patterson and Dr. Stoddard on board, he went through his preflight instrument check. Minutes later, engine starting, the plane rolled down the runway and took off into the gray sky.

China has many famed explorers. There was Zhang Qian,     1     traveled into Central Asia,     2     (open) corridors of trade that became the Silk Road. Zheng He was a great mariner in the 15th century. Yet these voyages     3     (undertake) under the direction of governments Xu Xiake was different.

Born in 1587, Xu Xiake grew up in a rich family. Yet he rejected the     4     （comfort) life to travel the lost world of imperial China. As one of the greatest land explorers, Xu Xiake is said     5     (travel) thousands of miles of Chinese mountains and rivers on foot in his lifetime. The written work of Xu Xiake's travel records and diaries contains some 404, 000 Chinese characters,     6     enormous work for a single author of his time. It mixes     7     (detail) of geography, botany and local history with the ratings of the Ming Dynasty lodgings (住宿).

“On the surface, Xu's travel can neither be classified as great affairs of state     8     great undertakings that changed the course of history.” writes the cultural historian Zheng Peikai. “Xu traveled to satisfy his own     9    (curious) — he traveled for the sake of traveling.”

Xu Xiake traveled across China for 34 years. Perhaps his     10    (great) journey was his last. At age 50, he traveled to the tropical frontiers of Yunnan. Hundreds of years later, we follow. Naturally, he is the father of Chinese backpacking.

10 . “Few articles change owners more frequently than clothes. They travel downwards from grade to grade in the social scale with remarkable regularity,” wrote the journalist Adolphe Smith in 1877 as he traced a coat’s journey in the last century: cleaned, repaired and resold repeatedly; cut down into a smaller item; eventually recycled into new fabric. But with the improvement in people’s living standards, that model is mind-boggling in the era of fast fashion. The average British customer buys four items a month. And it is reported that 350,000 tonnes of used but still wearable clothes go to landfills in the UK each year.

Yet the gradual revival of the second-hand trade has gathered pace in the past few years. At fashion website Asos, sales of vintage clothes (古董衫) have risen by 92%. Clothing was once worn out of necessity, and now it is simply a way of life. Busy families sell used items on eBay, teenagers trade on Depop and some fashion people offer designer labels on Vestiaire Collective. Strikingly, it has become big enough business that mainstream retailers (零售商) want a slice of the action.

For some buyers and sellers, the switch to the second-hand is born of financial difficulties. Only a few have become worried about the impact of their shopping habit on the planet. But the shift is only a partial solution. Some people worry that some mainstream brands may “greenwash” — using second-hand goods to improve their image, rather than engaging more seriously with sustainability.

However, the biggest concern may be that people keep buying because they know they can resell goods, still chasing the pleasure of the next purchase but with an eased conscience (愧疚). Boohoo, a powerful fast fashion company, has seen sales and profits rise, despite concerns about environmental problems in its supply chain that led to an investigation last year.

A new Netflix series, Worn Stories, documents the emotional meanings that clothes can have: Each old item is full of memories. Actually, a handbag from a grandmother and a scarf passed on by a father are both valuable for us. A love of style is not a bad or an unimportant thing. But a committed relationship is better than a quick flash. Can we learn to appreciate our own old clothes as well as others’?