Taking a math test can be pretty stressful. Even if you know the material, you can still get the problem wrong. Knowing how to go through your math test and check your work can save you from handing in a test full of mistakes that can be avoided. {#blank#}1{#/blank#}

Write it out

    You can also check a math problem by writing everything out on paper. {#blank#}2{#/blank#} Writing out math problems reduces your chances of missing anything to the lowest possible level, which is a common cause of incorrect answers.

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    Make sure your answers work by doing the opposite procedure of what your problem calls for, including the answer you got the first time around. In other words, you would use the opposite of this addition problem—subtraction (减法)—to determine whether or not your answer is the correct one.

Plugging in

    You may find that a variable isn't good enough or have a problem where you have to solve for a variable (变量). {#blank#}4{#/blank#} This is the only real way to assure yourself that the answer you've found is correct.

Check for a reasonable answer

    {#blank#}5{#/blank#} For example, if you get an answer in the millions and you know it should be in the thousands, you've likely misplaced a point. Go back through the work on your paper to make sure all of your formulas and calculations are correct. If everything looks okay, do the problem again and compare the result of the second try to what you've got on the first try.

    Do you still remember the haze（雾霾）in the winter? So many people got terribly ill during or after the haze. {#blank#}1{#/blank#}Here is advice for you to protect yourself in hazy weather.

    Spend less time outdoors.This is the most effective way for self-protection in such bad weather.With PM2.5 increasing 103mg per cubic meter,residents will risk a 2.29% increase of death,which experts found out in 2012.If you have to get out,avoid riding bicycles.{#blank#}2{#/blank#}

    Close your windows.Experts advice residents to avoid opening windows at home.If you have to ,avoid the time when smog is at its densest（浓的）.{#blank#}3{#/blank#}Besides,you can keep plants with broad leaves at home to absorb dust,and use air purifiers（清洁器）.

    Smoke less.{#blank#}4{#/blank#}In hazy weather,smoking would be even more harmful.Smokers are advised to keep their distance from cigarettes before the weather gets better.

    {#blank#}5{#/blank#}For example ,wear special masks outside to avoid breathing in PM2.5.Then take off your coat after getting indoors and keep it away from your other clean clothes,Don't forget to wash your face,rinse（漱）your mouth,and clean your nasal cavity（鼻腔）to clean the particulate matters（颗粒物）that fall on you.Last but not least,keep off stimulating（刺激性）foods.

A.Wear masks.

B.Pay attention to other daily things.

C.Also avoid rush hours,when pollutants will be denser.

D.That's because haze does harm to the health of people.

E.Cigarettes could cause more particulate matters,which are included in PM2.5 .

F.Take more fruits and vegetables instead,which are good for lung,spleen（脾）and kidney（肾）.

G.For residents who use air-conditioner,make sure your apartment has enough oxygen indoors.

    Eyesight（视力） plays a very important role in our daily life. Every waking moment, the eyes are working to see the world around us. Over forty percent of Americans worry about losing eyesight, but it's easy to include steps into our daily life to ensure healthy eyes. Here are five suggestions for a lifetime of healthy eyesight：

    Schedule（安排）yearly exams(检查). {#blank#}1{#/blank#} Experts advise parents to bring babies 6 to 12 months of age to the doctor for a careful check. The good news is that millions of children now can have yearly eye exams and following treatment, including eyeglasses.

    Protect against UV rays (紫外线). Long－term stay in the sun creates risk to your eyes. No matter what the season is, it's extremely important to wear sunglasses. {#blank#}2{#/blank#}

    Give your eyes a break. Two－thirds of Americans spend up to seven hours a day using computers or other digital products. {#blank#}3{#/blank#} Experts recommend that people practice the 20/20/20 rule: every 20 minutes, take a 20－second break and look at something 20 feet away.

    {#blank#}4{#/blank#} As part of a healthy diet, eat more fruits and vegetables each day. Vitamins (维生素) C and E help protect eyesight and promote eye health.

    Practice safe wear and care of contact lenses (隐形眼镜). Many Americans use contact lenses to improve their eyesight. While some follow the medical guidance for wearing contact lenses, many are breaking the rules and putting their eyesight at risk. {#blank#}5{#/blank#} Otherwise, you may have problems such as red eyes, pain in the eyes, or a more serious condition.

A．Eat your greens.

B．Eye care should begin early in life.

C．They can properly protect your eyes.

D．Stay in good shape by taking more vitamins.

E．Parents usually don't care about their own eyesight.

F．Always follow the doctor's advice for appropriate（适当的）wear.

G. This frequent eye activity increases the risk for eye tiredness.

How to deal with your homework

    Write it down.{#blank#}1{#/blank#} Make a note on your notebook. Always be sure to write down any homework for school so you won't forget anything.

    Create a homework station. Find somewhere comfortable and quiet to work.{#blank#}2{#/blank#} It will take twice as long to get the homework done. Shut off your cell phone, log off (退出) your computer (unless you will need it for your homework) and close the door.

    Do has early as possible. Don't leave homework to die last minute.{#blank#}3{#/blank#} The earlier you start your homework, the sooner you will finish! Do all your homework as early as you can, so you don't have a pile of (一堆) homework the next day.

    {#blank#}4{#/blank#} Think about how long it will take you to complete each homework subject. For example: English-ten minutes, science-ten minutes, math-forty minutes, history-twenty minutes.

    Treat yourself. You can easily get tired by sitting through an hour or two of homework without stopping. Once you finish homework for a subject, take a small break. Just make sure it's quick (no more than 15 minutes). Do not turn on the TV, or you'll never go back and finish your homework.{#blank#}5{#/blank#}

A. Use your time wisely.

B. Start as soon as you get home.

C. Start your hardest homework.

D. Never do your homework in front of the TV.

E. You can take a walk or find something to eat.

F. After short breaks, return to finish up the last of your work.

G. Keep a homework notebook where you record all your homework.

What is bitcoin?

    Bitcoin is a kind of digital currency, which means it doesn't exist as banknotes. At first, bitcoins were only made for collectors. {#blank#}1{#/blank#} You can store it in an online “wallet”. And with that wallet, you can spend bitcoin online and in the physical world for goods and services. More and more businesses, restaurants and universities included, accept payments in bitcoins. And, of course, bitcoin has a valuation, which you may have heard about because bitcoin's price has fluctuated up and down.

    What's different about bitcoin?

    {#blank#}2{#/blank#} That card is connected to information about you, such as your name and billing address. You can use bitcoin the same way, but unlike with a credit card, the trades you make with the currency are completely anonymous（匿名的）. They can't be used to identify you personally. {#blank#}3{#/blank#} Is that why the WannaCry attackers picked it as a form of payment?

    {#blank#}4{#/blank#}

    The bitcoin currency is unique—no authority can change the value. It's quick and easy to set up a bitcoin account. It's fast—it only takes a few minutes to transfer your payments. {#blank#}5{#/blank#}

    Possibly, Bitcoin has certainly gained fame in the news media as a technology that can result in crime. But even though the identities of people in a bitcoin trade may be hidden, the public ledger has increasingly helped law trace the movement of bitcoins from place to place.

A. What makes the bitcoin currency unique?

B. Another way of exchanging g bitcoins is at ATMs.

C. So you can use bitcoin to protect your privacy.

D. It's cheap—trade fees are usually zero, or less than 1 US cent.

E. Usually, if you pay for something on the Internet, you use a credit or debit card.

F. However, you can buy it with dollars or euros,, just like you can trade any other currency.

G. The bitcoin was introduced on the internet in 2008 by a software developer called Satoshi Nakamoto.

    Directions: Read the following passage. Fill in each blank with a proper sentence given in the box.

    Each sentence can be used only once. Note that there are two more sentences than you need.

    Are Your Clothes Causing Pollution?

    Very small pieces of plastic, called microfibers, are polluting rivers and oceans. {#blank#}1{#/blank#} Clothes worn for outdoor activities and exercise are often made of artificial material, which is useful in keeping warm. But they contain very small plastic fibers, which may also be harming the environment when you wash them. When people wash these clothes, very small pieces go down the drain with the wash water.

    Studies on microfibers in the environment

    Pollution caused by plastic is not new, but recent studies have shown the effect of microfibers in the environment. Studies show very small microfibers are ending up in our waters, which may come from waste water treatment factories. A 2015 study found them in fish from California.

    Microfibers, effect on food supplies

    Beyond the waterways, the researchers say microfibers may end up in soil and agricultural lands. {#blank#}2{#/blank#} This means there is much to be learned about microfibers and the environment. Some studies have shown that microfibers end up inside sea animals, like oysters. {#blank#}3{#/blank#} Researchers say that the fibers tend not to move into the tissue of the fish, but it needs more study.

    Steps to save or keep microfibers from the environment

    Until more information becomes known, there are steps to take to reduce the amount of microfibers in the environment. People should use less of the artificial materials. If we already have those in our lives and we're using them, an important step would be washing them less. {#blank#}4{#/blank#} A bag is being designed in which to wash these clothes. It traps the microfibers in the bag and it may be available for purchase soon.

A. New technology may also help.

B. So if these microfiber s have been found in fish and seafood, are they safe to eat?

C. They can also move around the atmosphere.

D. Studies are conducted on how much of the microfibers is released

E. The source of these microfibers may surprise you: your clothes.

F. Washing machines keep microfibers from escaping with w ash water.