Is there a magic cutoff period when offspring become accountable for their own actions? Is there a wonderful moment when parents can become spectators (旁观者) in the lives of their children and shrug, "It' s their life," and feel nothing?

    When I was in my twenties, I stood in a hospital corridor waiting for doctors to put a few stitches in my son's head. I was asked, "When do you stop worrying?" A nurse said, "When they get out of the accident stage." My mother just smiled faintly and said nothing.

    When I was in my thirties, I sat on a little chair in a classroom and heard how one of my children talked incessantly, disrupted (打断) the class, and was headed for a career making license plates. As if to read my mind, a teacher said, "Don't worry. They all go through this stage, and then you can sit back, relax, and enjoy them." My mother listened and said nothing.

    When I was in my forties, I spent a lifetime waiting for the phone to ring and the cars to come home, the front door to open.

    My friends said that when my kids got married I could stop worrying and lead my own life. I wanted to believe that, but I was haunted by my mother' s wan ( 淡淡的 ) smile and her occasional words, "You look pale. Are you all right? Call me the minute you get home."

    Can it be that parents are sentenced to a lifetime of worry? Is concern for one another handed down like a torch to blaze the trail of human frailties and the fears of the unknown? Is concern a curse? Or is it a virtue that elevates us to the highest form of life?

    One of my children became quite irritable recently, saying to me, "Where were you? I've been calling for three days, and no one answered. I was worried!!!"

    I smiled a wan smile.

阅读短文，从每题所给的四个选项（A、B、C和D）中，选出最佳选项。

    Human beings are the most intelligent of all animals because we are gifted with the ability to think and reason logically. Scientists and even common people with special intelligence have made a lot of inventions and contributions to modern lifestyle in the past. “Houses” have been the most popular area for discoveries and inventions in the past and even now.

    Many household items have been the result of inventions of people who desired better functioning of the existent products. Every individual has intelligence and if it is used properly for the right purpose it leads to invention of a new tool or device. Many new household inventions are made almost every day and there are specific companies, which particularly keep a record of all these inventions.

    A lot of inventions have been made recently in the household field. These products are patented(专利的) and have trade mark licenses. The patented sliding cinch is a very simple but effective method to prevent shoulder stress and injury for those who work before computers all day long. Vanity PC is a type of computer furniture that specifically hides all the computer wires and keeps a clean and good look. All the outdoor dust, mud and snow can be kept out of the house by installing(安装) the dirt drain(排水管) at the entrance of the door. Another important invention is the automatic toilet night-light, in which a small light starts when the lid of the toilet seat is opened and closes as soon as the lid is closed.

    These are some of the new household inventions invented mostly by common people. Thus, a variety of new household items are invented every day, which helps in a better functioning of household chores and in a more useful manner.

    Imagine that you're the creator and show runner of the newest comedy show on television. Only it isn't so popular yet, and your live Studio audience isn't giving you the big laughs the show deserves. Do you film the show all over again, hoping that this time the audience will laugh? Or is there another option for making a joke sound funnier than it was received?

    Sweeten(改善) the sound by adding a laugh track! “Sweetening,” or the addition of sound effects such as laughs, screams, and other audience-produced noises to the audio track of a TV show, has been used since the 1940s to produce the appearance, or rather the sound, of an engaged and entertained response to a show's comedy. Laugh tracks came into existence as not only a solution, and sometimes replacement, for an unengaged live audience but also as a way to engage an at-home audience into a more-traditional, public, and theaterlike experience. Adding a laugh track to a television show makes the viewers at home feel much less like they're sitting on a couch staring at the television screen and much more like they're in a room full of laughing happy people to varying degrees of success.

    Though the art of sweetening has risen and fallen in popularity over the past 60 years, credit for its creation and continued use is owed to laugh-track pioneer and sound engineer Charles Douglass. Douglass was the first to develop, in 1953, a machine for producing “canned laughter”, accessible at the push of a button or pull of a lever (操纵杆). Despite being artificial, sensibly edited laugh tracks are found by television studios to bring about a positive audience response, as their use is usually accompanied by higher ratings and increased audience memory. Though some television audiences may disagree with the value of the laugh track, the cheerful and repetitive sound holds a permanent place in the history and future of television comedy.

    Pyramid of Giza

    One of seven wonders of ancient world also becomes favorite site for astronomers to capture photographs from the orbit. It is not at all visible with naked eyes from space, so astronomers used special cameras for it.

    Grand Canyon

    It surely takes many days to enjoy every site of 277-mile-long Grand Canyon in Arizona. But the astronauts at orbits of Earth are able to see Grand Canyon with their own eyes all at once. The space images of Grand Canyon help the scientists to make surface map of the steep sided Canyon, also to monitor the changes within its surface.

    Ganges River Delta

    Ganges River Delta is 220 miles long; this amazing geographic feature can also seen from orbits of Earth. When the river becomes empty, it becomes the largest remaining habitat of Bengal tiger and other rich wild life.

    Palm Island, Dubai

    Palm Island along with world islands of Dubai can be seen even from space. The Palm Island actually holds two artificial island in shape of palm tree, spreading across in an area of 100,000 square meters. You can meet hundreds of luxury hotels and parks within this man-made wonder.

    After I mastered my first concerto (协奏曲) at the age of 14, my parents decided to get me a nice violin. I tried out dozens of instruments before I found my match: a German violin. It was beautiful, but what I liked best about it was its voice. Confident and strong, it was everything I longed to be.

    I'm not sure how much that violin cost, but my parents made me promise never to let it out of my sight. They didn't understand that pulling a large violin case ran counter to my daily middle school task of not being noticed. I was a strange, absent-minded kid. When I spoke up in class, my comments brought confused silence from teachers and wild laughter from students. Like a deer in a wolf pack, I tried to be quiet and still.

    However, my new violin was almost shockingly loud. Together, we were much louder than the rest of my middle school orchestra—which was encouraged, since the other kids made sounds like cats' crying. For one wonderful hour every day, I was showered with attention. Everyone wanted to hear what I had to say.

    Between classes, I bent under the combined weight of my violin case and a backpack filled with books. My body suffered, but my confidence grew. With my violin by my side, I found my voice. More and more, I contributed to class discussions and even made a couple of friends.

    Today, I'm just an excellent violinist with a regular day job. As I sit in my community orchestra, sometimes I feel jealous (嫉妒的) of my fellow musicians' instruments with their elegant voices. I may not be the best violinist around, but at least I'm still the loudest.

    There are two kinds of secrets: secrets of nature and secrets about people. Natural secrets exist all around us; to find them, one must study some undiscovered aspect of the physical world. Secrets about people are different: they are things that people don't know about themselves or things they hide because they don't want others to know. So when thinking about what kind of company to build, there are two distinct questions to ask: What secrets is nature not telling you? What secrets are people not telling you?

    It's easy to assume that natural secrets are the most important: the people who look for them can sound authoritative (权威的).This is why physics PhDs are difficult to work with—because they know the most basic truths, they think they know all truths. But does understanding electronic theory automatically make you a great marriage counselor? Does a gravity theorist know more about your business than you do? At PayPal, I once interviewed a physics PhD for an engineering job. Halfway through my first question, he shouted, "Stop! I already know what you're going to ask!" But he was wrong. It was the easiest no-hire decision I've ever made. Secrets about people are relatively overlooked. Maybe that's because you don^'t need a dozen years of higher education to ask the questions that uncover them: What are people not allowed to talk about? What is forbidden or taboo?

    The best place to look for secrets is where no one else is looking. Most people think only in terms of what they've been taught; schooling itself aims to spread basic wisdom. So you might ask: are there any fields that matter but haven't been standardized? Physics, for example, is a real major at all major universities, and it's set in its ways. The opposite of physics might be astrology, but astrology doesn't matter. What about something like nutrition? Nutrition matters for everybody, but you can't major in it at Harvard. Most top scientists go into other fields. Most of the big studies were done 30 or 40 years ago, and most are seriously flawed (有缺陷的). The food pyramid that told us to eat low fat and large amounts of grains was probably produced by Big Food(美国著名食品公司)than real science; its chief impact has been to worsen our obesity(肥胖)problem. There^'s plenty more to learn: we know more about the physics of far away stars than we know about human nutrition. It won't be easy, but it's not obviously impossible: exactly the kind of field that could produce secrets.