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Each year, more than 27 million American and Canadian kids get to school by bus. Most of those buses run on diesel（柴油）fuel, which give out pollution that riders can take in. Pollution levels can be several times higher inside a diesel school bus than outside it. Why? Pollution can leak in from the floor or blow in through windows.

An American government program started in 2012 offered schools money spent on cleaner school buses, but not all schools could get it. Five years later, emissions from buses in the winning districts fell. And a year after getting new buses, student attendance had improved in those districts. For an average district of 10,000 students, about six more students attended school each day in the winning districts, compared to the losing districts. Winning schools with higher rates of bus-riding kids had an average of 14 more students in class each day. And winning districts that replaced the oldest school buses? They had an average of 45 more students at school each day.

Those numbers may sound small, but they add up. And school attendance matters for students' achievements. Almost 3 million American kids ride school buses more than 20 years old. If American school districts had replaced all of those older buses, there would have been 1.3 million fewer student absences each year.

There might be other reasons for better attendance. For example, maybe kids preferred new buses. However, the most likely reason for fewer student absences was better health. A study done on adults showed that a brief exposure to diesel emissions reduced "network connectivity" in the brain. In other studies, such network-connectivity changes have been linked to worsened memory and mental tasks. A Washington State program upgraded pollution controls in old diesel buses. Afterward, fewer kids were hospitalized in those districts than in the schools without bus upgrades.

Almost all American school districts can apply for the program. But schools in low-income, tribal and rural areas will get priority. Kids in these areas tend to face the most health risks from older buses.

On March 1, Dr. Dituri began a project to stay for 100 days at a special hotel called Jules's Undersea Lodge 30 feet under the ocean surface in a conservation area in Key Largo.

The farther you go below the ocean's surface, the greater the pressure. Dr. Dituri wanted to learn how this pressure would affect the human body over time. He believes that high pressure could help people live longer and stay healthier as they get older. It could also help doctors treat different medical problems, including brain injuries.

While he was living underwater, Dr. Dituri still stayed busy daily according to his schedule. He often exercised in the morning. He kept teaching his college classes virtually and had online chats with over 5,500 students from 15 different countries. He also worked with ocean experts to figure out ways to preserve the ocean. He even had a number of visitors who dove down to spend a little time with him.

On June 9, De. Dituri returned to the surface with a new world record, beating the old record of 73 days. Many friends, family and other supporters were there to greet him and celebrate his success. Doctors quickly checked him out to make sure he was okay. Actually, Dr. Dturi went through several big changes. For one thing, he became 1.3 centimeters shorter during his time in the higher undersea pressure. Sleeping much better, his health greatly improved in a couple of ways. Dr. Dituri and his team plan to study the information they collected during the project. In November, Dr. Dituri will speak at an important medical meeting in Scotland about the discoveries the scientists made during the project.

Dr. Dituri says his favorite part of the project was talking with young people. "Who knows?" he said. "Maybe one day, one of them will come back and break the record we just set. My greatest hope is that I have inspired a new generation of explorers and researchers to push past all boundaries."

Italy is a wonderful destination in the world. This Italy trip-planning guide tells you where to go, what to see, and most importantly, what to eat!

The best time to visit

Springtime and early summer see mostly mild temperatures and crowds that range from moderate to dense. Summer is the most crowded season. Autumn is still packed, and the weather is pleasant. Generally speaking, wintertime is relatively less crowded.

Travel tips

Buy or reserve tickets in advance for those hot spots you want to see. But you may find restaurant service and trains that may run late. Take a deep breath, keep calm, just wait and adjust to the Italian slow style of life.

Italy is famous for pasta and pizza. At the seaside areas and on the islands, fresh seafood will dominate. Desserts are regional. Be sure to try some rare local cuisines wherever you are, rather than limiting yourself to familiar dishes.

Top cities to visit

Rome: The capital of Italy is home to Trevi Fountain, Piazza Venezia, National Roman Museum and so much more.

Florence: It is known for Michelangelo's David, the treasures of Uffizi Gallery, Ponte Vecchio bridge and leather goods at San Lorenzo Market.

Milan: Italy's fashion capital is also packed with important museums and is home to Leonardo da Vinci's Last Supper.

Venice: Boating on the Grand Canal, enjoying the glory of St. Mark's Square and seeing the smaller Venetian islands are popular.

About one hundred years ago, many educated people learned and spoke French when they met people from other countries. Today most people speak English when they meet foreigners.There are more people who speak English as a second language than people who speak English as a first language.Why is this?

One of them is that English has become the language of business. Another important reason is that popular American culture (like movies and music) has quickly spread throughout the world.

Is it good that English has spread to all parts of the world so quickly?It's important to have a language that the people of the earth have in common. Our world has become very global and we need to communicate with one another. On the other hand, English is a fairly complicated language to learn and it brings its culture with it. Do we really need that?

Scientists have already tried to create an artificial language that isn't too difficult and doesn't include any group's culture. It is called Esperanto.Maybe the popularity of English won't last that long either. There are more people in the world who speak Chinese than any other language. Maybe someday Chinese will be the new international language.