Getting older is a natural part of life. Changes as you get older are usually gradual. Certain physical changes are common. How fast your body can burn calories slows over time, which means that your body needs less food energy than before.

    How much and how well you sleep will likely change. Most people start needing reading glasses around forty, and many have some hearing loss later in life. Starting in your fifties, bone aging increase. How you feel as you get older depends on many things, including what health problems run in your family and the choices you make.

    If your family members have diseases or chronic (慢性的) health problems like high blood pressure, then you may have a greater chance of having those problems yourself. But it doesn't mean you will definitely have the same problems. Actually, the lifestyle choices you make can help reduce your chances of getting illness that run in your family. And even if you do get a family illness, choosing to be physically active, to eat healthy foods, and to learn how to deal with stress can keep the illness from destroying your ability to enjoy your golden years.

    What do you need to do to feel your best as you age? One of the most important things you can do for your health at any age is to be physically active. Physical activity keeps your body strong, and it helps with how you feel. People who stay active are less likely to get depressed.

    Your mental and emotional health is also important. Protect or improve your emotional health by staying in touch with friends, family, and the community. People who feel connected to others are more likely to feel happy than those who do not.

    All over the world people enjoy sports, Sports help to keep people healthy and happy, and to live longer.

    Many people like to watch others play games. They buy tickets or turn on their TVs to watch the games. Often they get very excited when "their" player or team wins.

    Some sports are so interesting that people everywhere go in for(参加) them. Football, for example, has spread(展开)around the world. Swimming is popular in all countries near the sea or in those with many rivers. What fun it is to jump into a pool or lake, whether in China, Egypt or Italy! And think of people in cold countries. Think how many love to skate or ski (滑雪) in Japan, Norway or Canada.

    Some sports or games go back thousands of years, like running or jumping. Chinese wushu, for example, has a very long history. But basketball and volleyball are rather new. Neither one is a hundred years old yet. People are inventing new sports or games all the time. Water-skiing is one of the newest in the family of sports.

    People from different countries may not be able to understand each other, but after a game together they often become good friends. Sports help to train(培养,训练) a person's character(性格,品格). One learns to fight hard but fight fair, to win without pride and to lose with grace(胜不骄，败不馁).

    Grey clouds move as low as smoke over the treetops at Lolo Pass. The ground is white. The day is June 10. It has been snowing for the past four days in the Bitterroot Mountains. Wayne Fairchild is getting worried about our trek over the Lolo Trail—95 miles from Lolo Montana to Weippe in Idaho, across the roughest country in the West. Lewis and Clark were nearly defeated 200 years ago by snowstorms on the Lolo. Today Fairchild is nervously checking the weather reports. He has agreed to take me across the toughest, middle section of the trail.

    When Lewis climbed on top of Lemhi Pass, 140 miles south of Missoula, on August 12, 1805, he was astonished by what was in front of him; "high mountain chains still to the West of us with their tops partially covered with snow." Nobody in what was then the US knew the Rocky Mountains existed, with peaks twice as high as anything in the Appalachians back East.

    Today their pathway through those mountains holds more attraction than any other ground over which they traveled, for its raw wilderness is an evidence to the character of two cultures: the explorers who braved its hardships and the Native Americans who prize and conserve the path as a sacred (神圣的) gift. It remains today the same condition as when Lewis and Clark walked it.

    The Lolo is passable only from July to mid-September. Our luck is holding with the weather, although the snow keeps getting deeper. As we climb to Indian Post Office, the highest point on the trail at 7, 033 ft, we have covered 13 miles in soft snow, and we hardly have enough energy to make dinner. After a meal of chicken, I sit on a rock on top of the ridge (山脊). There is no light visible in any direction, not even another campfire. For four days we do not see another human being. We are occupied with the things that mix fear with joy. In our imagination we have finally caught up with Lewis and Clark.

    The United States estimates that about one out of every 10 people on the planet today is at least 60 years old. By 2050, it's projected to be one out of 5. This means that not only will there be more old people, but there will be relatively fewer young people to support them.

    Professor Richard Lee of the University of California at Berkeley says this aging of the world has a great effect on economics. "Population aging increases the concentration of population in the older ages and therefore it is expensive," he said.

    Aging populations consume (消耗) more and produce less. With more people living longer, it could gel expensive. But Mr. Lee says with continuing increases in worker productivity and wise planning, it can be manageable.

    Societies have different methods for caring for the elderly，but each carries a cost Generally, there are three types of support Seniors can live off the wealth they gained when they were younger. They can rely on their family to take care of them, or they can rely on the movement.

    In industrialized nations, governments created publicly-funded (公共资助的) support systems. These worked relatively well until recent years, when aging population growth in places like the United States and Western Europe began to gradually weaken the systems' finances(资金). These nations now face some tough choices. Mr. Lee says the elderly in some of these countries must either receive less money, retire later or increase taxes to make the system continuable.

    Most developing nations haven't built this type of government-funded support, but have instead relied on families to care for their elderly. These nations also generally have a much younger population, which means their situation is not as urgent as more developed nations. But Mr. Lee says that doesn't mean they can pay no attention to the issue. "Third World countries should give very careful thought to this process, to population aging and how it may affect their economies — now, before population aging even becomes a problem," he explained.

    When your pen is broken, the batteries (电池) in your toys run out, or you have some leftover food, what will you do with these things? You will probably throw them all into one bin. But actually, all of these pieces of rubbish need to be sorted (分类) separately.

    Rubbish sorting is a big problem worldwide. In recent years, some Chinese cities have been working hard on it. Shanghai has worked with Alipay to create a "green account (账户)" service. Account owners get points by correctly sorting their rubbish. Through the Alipay app, they can exchange the points for milk, phone cards or other products. The city is asking all people living there to sort their rubbish into four groups: wet, recyclable, harmful and dry.

    Wet waste is something you don't want but that pigs can eat. Plastics, glass, paper and other things that can be reused are recyclable waste. Harmful waste includes things like medicine, batteries and bulbs. Finally, any waste that's not wet, recyclable or harmful will go in the "dry waste" bin.

    Many other Chinese cities are also sorting their rubbish in this way. For example, Shenzhen has been doing this since 2012. Students there also receive waste-sorting guidebooks that they must study.

    In fact, there are still many workers specially working for sorting rubbish by hand in China. There is still a long way to go. But it's never too late for every Chinese to learn how to sort rubbish properly and protect the environment.

    If you don't sort your rubbish, all of it will go to a landfill (垃圾填埋场) and be buried together.

    These landfills can take up much ground that could be used for planting. The electronic waste you throw away, such as batteries or used mobile phones, can cause pollution. Other pieces of rubbish, like the metal part of a pen, can be used to make other things if they are properly recycled.

On Monday, a scientist and doctor Robert Winston is to formally ask a question in congress about what assessments the government has made "for requiring adults riding bicycles in city centres to heave a licence and third-party insurance". The letter below is the entirely imagined response I would like the government to make to him.

Dear Robert,

You ask what assessments we've made for your proposal about obliging cyclists to have licences and insurance. The brief answer is: none. Nor do we have any plans to do so.

Why? Again, the short answer is this: it's a silly and pointless thing to suggest, as evidenced by the fact that practically no countries or territories anywhere in the world require cyclists to be licensed, or to have compulsory insurance.

I suppose it's only fair if I explain why I think it is such a non-issue. It's pretty simple: such a plan would achieve pretty much nothing, while causing significant problems. More widely, any sensible governments will do everything in their power to get more people cycling, not to put pointless obstacles in their way.

Let's just take one example. As I'm sure you know as a doctor, one of the problems facing our nation is that the National Health System is likely to collapse under the caring for an increasingly overweight population. Inactive living is central to this. Even a fairly brief daily bike trip can have miraculous benefits for people's health.

Next, how would such rules even work? Would the licensing and insurance be just for adults, or also children? How would the system even be enforced-would it also require all bikes to be registered with number plates?

Finally, what would you hope to achieve by this? If you believe licensing transport users stops wrongdoing, can I point to you the data showing how a third of drivers admit to using handheld phones while driving, despite the law forbidding it.

So, to summarize：your plan would be to introduce a hugely new administrative scheme that would most likely have limited effect on the behaviour of averagely law-abiding (守法的) transport users who rarely harm others, while putting people off from this beneficial type of transport.

I'm afraid I just don't get it.