Read the following article and select the best answer. Article: 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 , but the basic science is well understood. Each year, human activity causes billions of tons of greenhouse gases to be released 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 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 aren't carbon dioxide and the other greenhouse gases producing the warming that basic physics tells us they should be?" The only way to prove with 100% certainty that humans are responsible for global warming would be to run an experiment with two _ 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 certainty. Question: Which of the following can be the best title? - How can we stop global warming? - Where Is Global Warming Leading Us to? - Are Humans Definitely Causing Global Warming? - What's Relation of Global Warming and Greenhouse Gases?
Are Humans Definitely Causing Global Warming?

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Read the following article and select the best answer. Article: If you look at the night sky, you'll often see stars moving very quickly. In fact, they move much more quickly than they should according to their size and the laws of physics. Scientists do not completely understand why the speed of these stars is so high. But many believe the reason is that much of the universe is made of something called "dark matter". Groups of stars called galaxies, such as the Milky Way, might even be made up of 90 percent dark matter. How much something weighs depends on where it is. The same object weighs only half as much on Mars as it does on Earth and almost three times as much on Jupiter. So scientists prefer to talk about the mass of something rather than how much it weighs, because mass does not change. They can work out the mass of galaxies by measuring the distance between them and the speed they move at. Recently, Jorge Penarrubia, a senior academic at Edinburgh University, UK, and his team discovered something interesting: The mass of the Milky Way is only half as much as the mass of another nearby galaxy, Andromeda. This seems strange, and dark matter may explain why. Finding out more about dark matter could help us understand how the universe began, but this is not easy. Lots of scientists with different types of expert knowledge are working on the problem. We can't see dark matter, it's very difficult to measure and we can't find out its mass. Unlike stars, dark matter doesn't produce or reflect light. But we can make a good guess that it is there because of the way things move and the way light bends. Experts now think dark matter may be very different from the matter that we find on Earth. There may also be five times as much dark matter in the universe as ordinary matter. Question: The author mentions the masses of the Milky Way and Andromeda mainly to _ . - explain why the same object has a different weight on different stars - compare the distance between the Milky Way and Andromeda - show that studying dark matter could help to answer some scientific questions - support the idea that scientists prefer to talk about mass instead of weight
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show that studying dark matter could help to answer some scientific questions

Read the following article and select the best answer. Article: Dear Highlights Ask a question! E-mail it to letters @ Highlights, com. Gift Giving I'm going to China, and everyone in my chss is asking me to buy them something. What should I do? Reply from the Highlights Editors Your classmates arc probably just excited about your trip. Most likely they don't expect you to buy gifts for everyone. Sending a /cw postcards to the entire class during your trip would be a wonderful way to share your experiences. The pictures on the cards and your words of description will be thi' best gift of all. Dog Bagging My dog always begs for food at the dinner table. I really want to feed him, but my mom says I can't. I'm afraid he won't like me anymore. What should I do? Reply from the Highlights Editors Your dog loves you for many more reasons than just for what you feed him. You can show him that you care about him by playing with him, by petting him and speaking kindly to him. and by making sure he has fresh water. It might be best if your dog is not near the din!ner table while you are eating. You could teach him to stay in another room. Being BiHngua(> My aunt insists that we speak our language (Tagalog) at home and English outside the house. Do you think she is right? Reply from the Highlights Editors It is a great gift to have someone in your family who is willing to take the time to teach you another language. It's a good way to keep family traditions alive, and it helps to develop your language skills. Your ability to use both English and Tagalog will help you learn a third and fourth language later in life So it sounds like a great idea! Question: The Highlights editors snggest the student who is going to China_. - send postcards as the gifts to the class. - give each classmate a picture as a gift. - buy gifts for some of the classmates. - make phone calls to all the classmates.
send postcards as the gifts to the class.