The idea of being able to walk on water has long interested humans greatly. Sadly, biological facts prevent us ever accomplishing such a thing without artificial aid—we simply weigh too much, and all our mass pushes down through our relatively small feet, resulting in a lot of pressure that makes us sink.

    However, several types of animals can walk on water. One of the most interesting is the common basilisk Basilicus basilicus, a lizard (蜥蜴)native to Central and South America. It can run across water for a distance of several meters, avoiding getting wet by rapidly hitting the water's surface with its feet. The lizard will take as many as 20 steps per second to keep moving forward. For humans to do this, we，d need huge feet that we could bring up to our ears in order to create adequate w hitting. ''

    But fortunately there is an alternative : cornflour. By adding enough of this common thickening agent to water (and it does take a lot), you can create a “non-Newtonian” liquid that doesn't behave like normal water. Now, if the surface of the water is hit hard enough, particles(粒子）in the water group together for a moment to make the surface hard. Move quickly enough and put enough force into each step, and you really can walk across the surface of an adequately thick Liquid of cornflour.

    Fun though all this may sound, it's still rather messy and better read about in theory than carried out in practice. If you must do it, then keep the water wings handy in case you start to sink--and take a shower afterward!

根据短文内容，选择最佳答案，并将选定答案的字母标号填在题前括号内。

    Washington, D.C. Bicycle Tours

    Cherry Blossom Bike Tour in Washington, D.C.

    Duration Tour

    This small group bike tour is a fantastic way to see a world-famous cherry trees with beautiful flowers of Washington, D.C. Your guide will provide a history lesson about the trees and the famous monuments where they blossom. Reserve your spot before availability — the cherry blossoms—disappear!

    Washington Capital Monuments Bicycle Tour

    Duration:3 hours (4 miles)

    Join a guided bike tour and view some of the most popular monuments in Washington, D.C. Explore the monuments and memorials on the National Mall as your guide shares unique facts and history at each stop. Guided tour includes bike, helmet, cookies and bottled water.

    Capital City Bike Tour In Washington, D.C.

    Duration:3 hours

    Morning or Afternoon, this bike tour is the perfect tour for D. C. newcomers and locals looking to experience Washington, D.C. in a healthy way with minimum effort. Knowledgeable guides will entertain you with the most, interesting stories about Presidents, Congress, memorials, and parks. Comfortable bikes and a smooth tour route(路线）make cycling between the sites fun and relaxing.

Washington Capital Sites at Night Bicycle Tour

    Duration:3 hours(7miles)

    Join a small group bike tour for an evening of exploration in the heart of Washington, D.C. Get up close to the monuments and memorials as your bike the sites of Capitol Hill and the National Mall. Frequent stops are made for photo taking as your guide offers unique facts and history. Tour includes bike, helmet, and bottled water. All riders are equipped with reflective vests and safety lights.

    When school started on that warm August day, I threw myself into everything I did, including playing volleyball. I decided to become beautiful, or at the very least, skinny. I stopped eating completely. Soon I began losing weight, which thrilled me, and I even grew to love the tiredness and lightheadedness( 头晕)that came with my poor diet, for those feelings meant that I was winning.

    As the season progressed, things had become tense between my head volleyball coach, Coach Smith, and me. She felt that something was wrong with my health. She talked with me about my eating and was angry that I wouldn't listen to her when she tried to make me eat. She tried to persuade me in a determined way and so we fought constantly. Then my hunger started to affect my performance. I was so tired that practice and games were becoming a struggle. One afternoon, with hurt in her eyes, Coach Smith asked me what I had eaten and I told her nothing yet. She looked at me, disappointment in her eyes, knowing she couldn't make me stop, and walked away.

    A couple of weeks later I attended a formal dinner for our volleyball team. I stood there as my coach managed to say something nice about me. I realized then that I had ruined my senior year by being disrespectful, and I had probably ruined hers as well. So that evening I wrote her a letter apologizing and thanking her.

    Then one Saturday, as I was reading in the library, I felt someone gently take my arm and say softly, “Lynn Jones, how are you doing?” I looked up and saw the familiar face. “Thanks for the letter,” she said. “It meant a lot.” When I think of a coach, I think of someone above me, someone who gives instruction — not a friend. But Coach Smith is different, and, like any other good friend, she dealt with my problem in a determined way even when I hated her for it at that time. I didn't deserve her kindness, but she gave it anyway. I will forever be grateful for her help, and now for her friendship.

    Two of the saddest words in the English language are "if only". I live my life with the goal of never having to say those words, because they convey regret, lost opportunities, mistakes, and disappointment.

    My father is famous in our family for saying, "Take the extra minute to do it right. "I always try to live by the "extra minute" rule. When my children were young and likely to cause accidents, I always thought about what I could do to avoid an "if only" moment, whether it was something minor like moving a cup full of hot coffee away from the edge of a counter, or something that required a little more work such as taping padding (衬垫) onto the sharp corners of a glass coffee table.

    I don't only avoid those "if only "moments when it comes to safety. It's equally important to avoid "if only" in our personal relationships. We all know people who lost a loved one and regretted that they had lost an opportunity to say "I love you" or "I forgive you". When my father announced he was going to the eye doctor across from my office on Good Friday, I told him that it was a holiday for my company and I wouldn't be there. But then I thought about the fact that he's 84 years old and I realized that I shouldn't give up an opportunity to see him. I called him and told him I had decided to go to work on my day off after all.

    I know there will still be occasions when I have to say "if only "about something, but my life is definitely better because of my policy of doing everything possible to avoid that eventuality (不测的事) . And even though it takes an extra minute to do something right, or it occasionally takes an hour or two in my busy schedule to make a personal connection, I know that I' m doing the right thing. I'm buying myself peace of mind and that's the best kind of insurance for my emotional well-being.

    Scientists have found evidence of a link between social and economic status and childhood attention deficit disorder(ADHD)(注意力缺陷多动障碍)in the UK. A team led by the University of Exeter Medical School analysed data from the Millennium Cohort Study, a database of more than 19, 500 UK children born between 2000 and 2002 .The study was published in the Journal of Child Psychology and Psychiatry.

    Findings showed that more children with ADHD came from families below the poverty line than the UK population as a whole, with average family incomes for households whose study child was affected by ADHD at £324 per week, compared to £391 for those whose child was not. The study found the odds (机会)of parents in social housing having a child with ADHD was roughly three times greater than for those who owned their own homes.

    The team also found that the odds of younger mothers having a child with ADHD were significantly higher than for other mothers. Mothers with no qualifications were more than twice as likely to have a child with ADHD than those with degrees, and lone (孤独的)parents were more likely to have a child with ADHD diagnosis than households with two live-in parents.

    Information was gathered from surveys when the cohort children were nine months old, and at the ages of three, five, seven and eleven.

    Dr Ginny, of the University of Exeter Medical School, who led the study, said, "There is a genetic element to ADHD, but this study provides strong evidence that ADHD is also associated with a disadvantaged social and economic background. Some people believe that ADHD in children causes disadvantage to the economic situation of their family, but we found no evidence to support that theory. It's important to discover more about the causes of this disorder so that we can look towards prevention, and so that we can target treatment and support effectively. "

    A great number of species make their home in the vast waters of the Atlantic Ocean. Although the entire ocean makes up an ecosystem, many smaller habitats are found within, including an open-water habitat off the coast of the Northern Atlantic Ocean known as the Sargasso Sea. Sargassum is an alga(海藻) that floats in masses that can continue for miles. The waters of the Gulf Stream push the water in a northward move into this area. This constant move and varying temperature support the accumulation of the brown-colored seaweed.

    The Sargasso Sea is so enormous that one method of information collection has not been enough for scientists to obtain an accurate picture of what takes place within this ecosystem. Researchers have needed to employ several methods of sampling. Methods such as dragging nets over the surface of the water and videotaping beneath areas of sargassum have served scientists well. Information collected has shown that the Gulf Stream pushes brown algae from open water into the Sargasso Sea area, creating a diverse floating habitat in an area that would otherwise not support that wildlife.

    In the most recent study of the sargassum community off the shores of North Carolina, eighty-one fish species were documented as using the area as a microhabitat. This is an increase from previous studies. The types of fish found here are both commercially and environmentally important. The South Atlantic Fishery Management Council is working to regulate the harvesting of sargassum. The Council hopes to have the area classified as an Essential Fish Habitat. Which would afford it certain protections.

    Further research needs to be done before scientists understand how to best protect the Sargasso Sea as well as understand how it goes about supporting so many important types of wildlife.