On Monday, the Centers for Disease Control and Prevention predicted that 42% of Americans could be overweight by 2030. Our expanding waistlines lead to not only a medical problem, but according to a recent article In The New York Times, it could also endanger personal safety in some situations—in an airplane crash, for example.

    The New York Times' Christen Negroni reports that engineers and scientists are questioning whether airplane seats are adequately constructed to protect overweight travelers. Government standards for airplane seat strength（强度）— first set moe than 60 years ago — require that the seats be made for a passenger weighing 170 pounds (77kg). Today, the average American man weighs nearly 194 pounds (88kg) and the average woman 165 pounds (75kg). Negroni reports:

    “If a heavier person completely fills seat, the seat is not likely to behave as intended during a crash,” said Robert Salazar, the leading scientist at the Center for Applied Biomechanics at the University of Virginia. “The energy absorption that is built into the aircraft seat is likely to be overpowered and the passengers will not be protected properly.”

    “Nor would the injury be limited to that passenger only,” Dr. Salzar said. “If a seat or a seat belt fails,” he said, “those people who are seated nearby could be endangered from ‘the uncontrolled movements of the passenger'.”

    Most complaints about airplane seats focus on their lack of comfort and high ticket price, and whether overweight passengers should be made to buy two seats. But The New York Times' article brings up another reason to feel anxious about flying. Investigators of the issue got in touch with the airplane seat and seat belt makers, but they refused to comment on the problem. Experts agreed that crash testing should be done with overweight dummies （人体模型）. Both airplane seats and seat belts should be tested, they said.

    Fortunately, however, according to Nora Marshall, a senior adviser at the National Transportation Safety Board, the board's investigators have never seen an accident involving a commercial plane in which the weight of a passenger was a problem.

阅读下列短文，从每题所给的四个选项（A、B、C和D）中选出最佳选项。

    Students from Florida International University in Miami walked on water Thursday for a class assignment. To do it, they wore aquatic (水上的) shoes they designed and created.

    Alex Quinones was the first to make it to the other side of a 175-foot lake on campus in record time—just over a minute. Quinones, who wore big boat-like shoes, also won last year and will receive $500.

    Students had to wear the aquatic shoes and make it across the lake in order to earn an “A” on the assignment for a special course. “It's traditional in a school of architecture to do boats out of cardboard (硬纸板) for a boat race. I thought our students were a little bit more special than that,” Canaves said. “We decided to do the walk on water event to take it to the next level.”

    A total of 79 students competed in the race this year in 41 teams. Only 10 teams failed to cross the lake. Others who fell got back up and made it to the end. The race is open to all students and anyone in the neighborhood. The youngest person to ever took part was a 9-year-old girl who competed in place of her mother, while the oldest was a 67-year-old woman. A large crowd on campus joined Canaves as he cheered on the racers. He shouted encouraging words, but also laughed as some unsteadily made their way to the end.

    “A part of this is for them to have more understanding of designing and make it work better,” he said. It is also a lesson in life for the students.

    “Anything, including walking on water, is possible, if you do the research, test it and go through the design process seriously.

    Do you often feel tired? Is it really because of the large amount of mental work you do? Here is an astonishing and significant fact: Mental work alone can't make us tired. It sounds absurd. But a few years ago, scientists tried to find out how long the human brain could labor without reaching a stage of fatigue (疲劳). To the amazement of these scientists, they discovered that blood passing through the brain, when it is active, shows no fatigue at all! If we took a drop of blood from a day laborer, we would find it full of fatigue toxins(毒素) and fatigue products. But if we took blood from the brain of an Albert Einstein, it would show no fatigue toxins at the end of the day.

    So far as the brain is concerned, it can work as well and swiftly at the end of eight or even twelve hours of effort as at the beginning. The brain is totally tireless. So what makes us tired?

    Some scientists declare that most of our fatigue comes from our mental and emotional attitudes. One of England's most outstanding scientists, J.A. Hadfield, says, “The greater part of the fatigue from which we suffer is of mental origin. In fact, fatigue of purely physical origin is rare.” Dr. Brill, a famous American scientist, goes even further. He declares, “One hundred percent of the fatigue of a sitting worker in good health is due to emotional problems.”

    What kinds of emotions make sitting workers tired? Joy? Satisfaction? No! A feeling of being bored, anger, anxiety, tenseness, worry, a feeling of not being appreciated —— those are the emotions that tire sitting workers. Hard work by itself seldom causes fatigue. We get tired because our emotions produce nervousness in the body.

    A mother stared down at her son who was dying of terminal leukemia (白血病). Like any parent she wanted her son to grow up and realize all his dreams. She took her son's hand and asked, "Bopsy, did you ever think about what you wanted to be when you grew up?"

    "Mommy, I always wanted to be a fireman when I grew up."

    Mom smiled back and said, "Let's see if we can make your wish come true." Later that day she went to her local fire department in Phoenix, Arizona, where she met Fireman Bob. She explained her son's final wish and asked if it might be possible to give her six-year-old son a ride around the block on a fire engine. Fireman Bob said, "Look, we can do better than that. If you'll have your son ready at seven o'clock Wednesday morning, well make him an honorary fireman for the whole day, He can come down to the fire station; eat with us, go out on all the fire calls, the whole nine yards! And, if you'll give us his sizes, we'll get a real fire uniform made for him."

    Three days later Fireman Bob picked up Bopsy, dressed him in his fire uniform and escorted（护送）him from his hospital bed to the waiting hook and ladder truck. Bopsy got to sit up on the back of the truck and help steer it back to the fire station. He was in heaven.

    There were three fire calls in Phoenix that day and Bopsy got to go out on all three calls. He rode in the different fire engines and even the fire chief's car. Having his dream come true, with all the love and attention that was lavished（慷慨给予）upon him, Bopsy lived three months longer than any doctor thought possible.

    One night all of his vital signs began to drop and the head nurse began to call the family members to the hospital. Then she remembered the day Bopsy bad spent as a fireman, so she called the fire chief and asked if it would be possible to send a fireman in uniform to the hospital to be with Bopsy as he made his transition. The chief replied, "We can do better than that. We'll be there in five minutes. Will you please do me a favor? When you hear the sirens（警报器）screaming and see the lights flashing, will you announce over the PA system that it's just the fire department coming to see one of its finest members one more time? And will you open the window to his room? Thanks?"

    About five minutes later a hook and ladder truck arrived at the hospital, extended its ladder up to Bopsy's third floor open window and 14 firemen and two fire-women climbed up the ladder into Bopsy's room. With his mother's permission, they hugged him and held him and told him how much they loved him. With his dying breath, Bopsy looked up at the fire chief and said, "Chief, am I really a fireman now?"

    "Bopsy, you are," the chief said. With those words, Bopsy smiled and closed his eyes for the last time.

    Started in 1636, Harvard University is the oldest of all the many colleges and universities in the United States. Yale, Princeton, Columbia and Dartmouth were opened soon after Harvard.

    In the early years, these schools were much alike. Only young men went to colleges. All the students studied the same subjects, and everyone learned Latin, Greek and Hebrew. Little was known about science then, and one kind of school could teach everything that was known about the world. When the students graduated, most of them become ministers or teachers.

    In 1782, Harvard started a medical school for young men who wanted to become doctors. Later, lawyers could receive their training in Harvard's law school. In 1825, besides Latin and Greek, Harvard began teaching modern languages, such as French and German. Soon it began teaching American history.

    As knowledge increased, Harvard and other colleges began to teach many new subjects. Students were allowed to choose the subjects that interested them.

    Today there are many different kinds of colleges and universities. Most of them are made up of smaller schools that deal with special fields of learning. There's so much to learn that one kind of school can' offer it all.

    The earliest known copy of Leonardo da Vinci's Mona Lisa—thought to have been painted at the same time as the original masterpiece—has been discovered at the Prado Museum in Madrid, Spain. The work offers art-lovers an attractive clue to what the model for the world's most famous painting really looked like. Controllers of the museum found the picture hidden beneath layers of paints during restoration work on a picture initially thought to have been a later replica(exact copy) of the Mona Lisa.

    The restored version shows the same woman that Leonardo depicted (描画), against a landscape similar to that shown in the background of the original, which now hangs in the Louvre in Paris. And while the features of Leonardo's Mona Lisa have been dulled by centuries of dirt and layers of cracked paints—which are unlikely ever to be removed—in the recently-rediscovered copy, she appears fresher-faced and younger than her better-known "twin".

    News of the find was revealed at a meeting at London's National Gallery, linked to its "Leonardo da Vinci: Painter at the Court of Milan" exhibition. "This sensational (轰动的) find will transform our understanding of the world's most famous picture," the Art Newspaper reported, adding that the clues found on the Madrid version suggest that the original and the copy were begun at the same time and painted next to each other, as the work went on.

    Miguel Falomir, manager of Italian painting at the Prado, told reporters that expert analysis suggested a strong link between Leonardo and the artist who painted the copy. "The painting was done in the painter's own workshop," he said. "It is absolutely consistent with Leonardo's work, but Leonardo didn't actually do any work on it himself."