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    If you could change your child's DNA in the future to protect them against diseases, would you? It could be possible because of technology known as CRISPR-Cas, or just CRISPR.

    CRISPR involves a piece of RNA, a chemical messenger, designed to work on one part of DNA; it also uses an enzyme (酶) that can take unwanted genes out and put new ones in, according to The Economist. There are other ways of editing DNA, but CRISPR will do it very simply, quickly, and exactly.

    The uses of CRISPR could mean that cures are developed for everything from Alzheimer's to cancer to HIV. By allowing doctors to put just the right cancer-killing genes into a patient's immune system, the technology could help greatly.

    In April scientists in China said they had tried using CRISPR to edit the genomes (基因组) of human embryos. Though the embryos would never turn into humans, this was the first time anyone had ever tried to edit DNA from human beings. With this in mind, the US' National Academy of Sciences plans to discuss questions about CRISPR's ethics (伦理问题).

    For example, CRISPR doesn't work properly yet. As well as cutting the DNA it is looking for, it often cuts other DNA, too. In addition, we currently seem to have too little understanding of what DNA gives people what qualities.

There are also moral questions around “playing God”. Of course, medicine already stops natural things from happening —— for example, it saves people from infections. The opportunities to treat diseases make it hard to say we shouldn't keep going.

    A harder question is whether it is ever right to edit human germ-line (种系) cells and make changes that are passed on to children. This is banned in 40 countries and restricted in many others. However, CRISPR means that if genes can be edited out, they can also be edited back in. It may be up to us as a society to decide when and where editing the genome is wrong.

    Also, according to The Economist, gene editing may mean that parents make choices that are not obviously in the best interests of their children: “Deaf parents may prefer their children to be deaf too; parents might want to make their children more intelligent at all costs.”

    In the end, more research is still needed to see what we can and can't do with CRISPR. “It's still a huge mystery how we work,” Craig Mello, a UMass Medical School biologist and Nobel Prize winner, told The Boston Globe. “We're just trying to figure out this amazingly complicated thing we call life.”

    Recently,people in US education have gotten extremely worried because a new report has shown that American students have a math problem.

    The 2015 Program for International Student Assessment（评估）(PISA) shows math scores in the US getting lower and no improvement in science or reading.PISA tests 15-year-olds from different countries and regions in their math,science and reading skills.About 540,000 students from 72 countries and regions took part in the assessment in 2015.

    US scores in reading and science were about the same as three years ago,leaving Americans near the middle of the bigger group.But the situation in math is much more worrying.The US average score was 470,be;ow the OECD（经合组织）test average of 490,meaning the US was No.40 among the 72 countries and areas.It was 12 points lower than in 2012 and 18 points lower than in 2009.So,what is going on with American students' math skills?

    One reason may be that the US does not teach math in enough depth."Students are often good at answering the first part of a problem in the United States,"said Andreas Schleicher,director of education and skills at OECD."But as soon as students have to go deeper and answer the more complicated part of a problem,they have difficulties."In comparison,many high-performing countries and regions in math teach a lot less but focus in much greater depth, especially when you look at East Asia,Japan and Singapore,according to Schleicher.

    Another reason may be the fact that many people in the US are unwilling to travel to foreign countries to learn better teaching practices."One of our biggest challenges in the US is that the teachers are not going out and seeing what high-performing countries do differently,"said Wendy Kopp,who started Teach for America,in a news program.

    Do you want to go abroad to make money? If you've decided to invest（投资）overseas, you may be wondering which countries are the best, and which countries will give you the biggest returns. In some locations, investment is easier than others. Here are the top 4 best countries to invest in housing:

    Italy

    A charming hillside area, Abruzzo makes for a great investment. This beautiful place has lots of local housing resources, and you can buy a home that needs just $45,000. With proper repair, selling for at least four times that much, you can easily make money.

    Argentina

    Central America's Argentina's tourism is popular, so it has a lot to offer locals and tourists alike. This coastal country is affordable, too, especially in the busy city of Buenos Aires. As the city is rapidly expanding, now it's time to get this hot investing opportunity.

    Mexico

    In the south of the border, you can find unbelievable investment. Playa del Carmen will give you the most for your money. Plus its tourism is popular and it's a nice place to visit and easily accessible from the United States.

    Panama

    Historic and lively, Panama is a safe place for shopping. You'll enjoy great tax（税金）benefits in Panama. Panama does not charge income tax for the first 10 years of your investment.

        No matter where you choose to buy, these four countries will provide you with a great location and return on investment.

    Dream is strength. The strength can bring us wherever we want to get to and it can bring us a lot of wonders on our way to the place in our dreams.

    Dream is beauty. Maybe you can see the things full of magic and maybe you will be moved by your own dream.{#blank#}1{#/blank#}. But should we have our life without dreams? Of course not.

    Everyone has his dreams and dreams are especially important to teenagers. As teenagers, you have many dreams. These dreams can be very big, such as winning the Nobel Prize. Or they can be small, for example, you may just want to become one of the ten best students in your class. {#blank#}2{#/blank#}, what do you do with it? Do you ever try to make your dream come true?

    Andrew Matthews, an Australian writer, tells us that making our dreams come true is the biggest challenge in our life. {#blank#}3{#/blank#}, or that it is impossible for you to become a writer.{#blank#}4{#/blank#}. In fact, everyone can fulfill his dream. The first thing you must do is remember what your dream is. Don't let it leave your heart. Keep telling yourself what you want. Do this step by step and your dream will come true earlier because a big dream is made up of many small dreams.

    You must never give up your dreams.{#blank#}5{#/blank#}. But the biggest one comes from yourself. You need to decide what is the most important and face all these difficulties bravely.

A. These kinds of thoughts stop you realizing your dream

B. There will be many difficulties on the road to your dreams

C. Once you find a dream

D. You may think you're not very good at some school subjects

E. Both big dreams and small ones are very important to our lives

F. The world is so real that the dreams seem weak

G. Your talent is one of the most important factors in living your dreams

    After disappearing for over 19 years, measles (麻疹) is making a comeback in America. Since January 2019, the disease has infected more than 700 people, mostly small children, and the number seems to be increasing daily.

    Measles is an infectious disease that typically begins with a high fever, cough, runny nose, and red, watery eyes. Many people also lose their appetites and feel sleepy. About three to four days after the symptoms start, the person breaks out into a rash (皮疹) that begins on the face at the hairline and then spreads to the neck and the rest of the body.

    In healthy people, the recovery, which takes between two to three weeks, starts soon after the rash begins. However, for about 40 percent of patients ­ mainly kids under the age of five or older adults ­ the disease often leads to pneumonia (肺炎), which, if left untreated, could result in death.

    The recent outbreak is thought to have been caused by travelers picking up the virus in a country where the disease is still existing and exposing it to an unvaccinated (未接种的) community in the US. In New York, it was carried back by someone who had recently visited Israel, which is currently undergoing a significant measles, while in Washington, "patient zero" was infected by a type that is currently circulating in Europe.

    To limit the spread of the disease before it gets out of hand, US health officials are attempting to educate communities with high rates of unvaccinated children. They are also urging adults to consult with their physicians and get injected if considered necessary by the doctor.

    Hopefully, health officials worldwide will be able to convince parents that vaccinating their children will protect, not harm, them.