阅读理解

　　Just as the world's most respected scientific bodies have confirmed that the world is getting hotter, they have also stated that there is strong evidence that humans are driving the warming．Countless recent reports from the world's leading scientific bodies have said the same thing．For example, a 2010 summary of climate science by the Royal Society stated that：“There is strong evidence that the warming of the Earth over the last half-century has been caused largely by human activity．”

　　The idea that humans could change the planet's climate may be counter-intuitive(与直觉不符的), but the basic science is well understood．Each year, human activity causes billions of tons of greenhouse gases to be released(释放)into the atmosphere．As scientists have known for years, these gases hold heat that would otherwise escape to space, wrapping the planet in an invisible blanket．

　　Of course, the planet's climate has always been changing thanks to “natural” factors(因素)such as changes in solar or volcanic activity, or cycles relating the Earth's going around the sun．According to the scientific literature, however, the warming recorded to date matches the pattern of warming we would expect from a build-up of greenhouse gas in the atmosphere – not the warming we would expect from other possible causes．

　　Even if scientists did discover another reasonable explanation for the warming observed so far, that would beg a difficult question．As Robert Henson puts it in The Rough Guide to Climate Change：“If some newly discovered factor can account for the climate change, then why can't carbon dioxide and the other greenhouse gases?

　　The only way to prove with 100％ certainty that humans are responsible for global warming would be to run an experiment with two identical Earths –　one with human influence and one without．That obviously isn't possible, and so most scientists are careful not to state human influence as an absolute certainty．

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阅读理解

　　In my profession as an educator and health care provider, I have worked with numerous children infected with the virus that causes AIDS．The relationships that I have had with these special kids have been gifts in my life．They have taught me so many things, but I have especially learned that great courage can be found in the smallest of packages．Let me tell you about Tyler．

　　Tyler was born infected with HIV：his mother was also infected．From the very beginning of his life, he was dependent on medications to enable him to survive．When he was five, he had a tube surgically inserted in a vein in his chest．This tube was connected to a pump, which he carried in a small backpack on his back．Medications were hooked up to this pump and were continuously supplied through this tube to his bloodstream．At times, he also needed supplemented oxygen to support his breathing．

　　Tyler wasn't willing to give up one single moment of his childhood to this deadly disease．It was not unusual to find him playing and racing around his backyard, wearing his medicineladen backpack and dragging his tank of oxygen behind him in his little wagon．All of us who knew Tyler marveled at his pure joy in being alive and the energy it gave him．Tyler's mom often teased him by telling him that he moved so fast that she needed to dress him in red．That way, when she peered through the window to check on him playing in the yard, she could quickly spot him．

　　This dreaded disease eventually wore down even the likes of a little dynamo like Tyler．He grew quite ill and, unfortunately, so did his HIV－infected mother．When it became apparent that he wasn't going to survive, Tyler's mom talked to him about death．She comforted him by telling Tyler that she was dying too, and that she would be with him soon in heaven．

　　A few days before his death, Tyler beckoned me over to his hospital bed and whispered, “I might die soon．I'm not scared．When I die, please dress me in red．Mom promised she's coming to heaven, too．I'll be playing when she gets there, and I want to make sure she can find me．”

[解题导语]　作者与无数艾滋病患儿打过交道，这些患儿使作者明白了很多道理。其中，作者遇到一个叫泰勒的小患者，他面对死神与厄运的坦然与乐观给作者留下了深刻印象。

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