There are 115 distinct (独特的) species of pine trees with 35 native to North America. Pines are defined as evergreens with long, needle-like leaves and are only native to the northern hemisphere. Pine trees are an adaptable and tough species that can survive in many conditions where other plants cannot. The average pine tree is 45 to 60 feet tall, but some are nearly twice as high.

Western White Pine

    The western white pine grows the tallest of any pine tree, reaching up to 110 feet in height. They have blue-green needles arranged in bundles (束) of five and produce a long cone (球果).

Bristlecone Pine

    The bristlecone pine grows slowly, reaching about 20 feet tall. It is one of the oldest species of pine.

Mexican Pine

    The Mexican pine can grow to 50 feet tall, with long, slender needles that drape (下垂) off it like a weeping willow (柳树). Often nicknamed the “willow pine”, it is native to Mexico. Its leaves can droop up to 12 inches long.

Sugar Pine

    The sugar pine is another of the large pine species, such as the bull pine, but it also has the largest cones of any pine species, at 10 to 20 inches long. It grows from Oregon to California and is often used for construction.

Jack Pine

    The jack pine is one of the smallest species of pine with rare leaves. Compared with the pines mentioned above, it doesn't seem to belong in the family. It is considered a member of the scrub-pine family; it prefers sandy soil.

How to Improve Vocabulary Fast

    Your vocabulary refers to the words in a language you are familiar with. We should learn some ways to expand it.

    Read every day. {#blank#}1{#/blank#} Choose reading material that is slightly above your level and keep a dictionary with you to look up words you do not know.

    {#blank#}2{#/blank#} If you do not meet with an unfamiliar word in your daily reading, use your dictionary to search for one.

    Learn the correct definition and pronunciation for each new word. Pronunciation is as important as definition because in order to add a word to your active vocabulary, you must be able to use it in speech.

    Elaborate(阐释)on the meaning of the word. Use imagery and personal relevance. If you have just learned that the word “stubborn” , think about the neighbor who will not lend you his car. {#blank#}3{#/blank#}

    Use your new word in speech and in writing. E-mail your sister about how your cat is stubborn about sleeping on your pillow. {#blank#}4{#/blank#} But the more you use it, the more fluent you will become in its use. Soon it will be a regular part of your active vocabulary.

    Tell everyone you are trying to increase your vocabulary. Encourage them to ask you what your latest word is {#blank#}5{#/blank#}.The more you explain the meaning of a word to someone, the more likely you are to remember it.

A. Or let them ask for the definition of a new word you have used.

B. Your vocabulary contains the words you understand.

C. The vocabulary can be increased.

D. Imagine him shaking his head, and think of him as “stubborn in his refusal”.

E. The first time you use a new word in speech it may seem strange.

F. Find a new word every day.

G. The more often you read, the faster your vocabulary can grow.

    We all have to make decisions all the time, and we have an abundance of choices, ranging from tiny issues to vital ones. Unfortunately, people often find it hard to make decisions{#blank#}1{#/blank#} If you would like to improve your skill of decision making, here are four suggestions for you. Don't expect to have it all.

    {#blank#}2{#/blank#} You can't order every delicious dish on the menu. And there will be paths not taken, careers not chosen, to name a few. You can imagine some “what if' situations if you must, but do not let them take up too much space in your brain.

    {#blank#}3{#/blank#}

    It's often good to think through your decisions. But don't overdo it. Research can reach a point where returns begin to reduce, which makes it confusing more than clarifying. Many good decisions can be made based as much on intuition (直觉) as on careful assessment of endless data.

    Don't delay making decisions.

    Yes, there is a time to put off making a decision. Perhaps you need more information{#blank#}4{#/blank#} Or it's likely that you wait for a less stressful time. Just don't wait so long that the decision is made by your own indecisiveness.

    Don't be hard on yourself.

    You decide to go on a voyage. You choose an expensive liner. Everything should work out just right. Only you didn't expect a bug that ran around on the ship, making you and your family sick for five days{#blank#}5{#/blank#}But please remember it is unavoidable sometimes.

A. Don't spend too much time thinking.

B. It is an important source of information.

C. Don't count on emotion to make decisions.

D. Maybe you wish to consult with your advisor.

E. You may regret making such a stupid decision.

F. That means the skill of good decision-making counts a lot.

G. Decisions force us to close the door on other possibilities.

    Palaces are known for their beauty and splendor, but they offer little protection against attacks. It is easy to defend a large building, but usually these buildings are not designed with the comfort of a king in mind. When it comes to structures that are both beautiful and defensive, the European castle is a big success.

    Castles were originally built in England by the Normans in 1066. They built towers and walls to secure the land they had taken. These castles provided the Normans with a quiet and safe place. They also served as bases of operation for attacks. In this way castles served both defensive and offensive roles. Besides, castles served as offices for governors. Those that were socially beneath the governor would come to report affairs and express their respect. They would address problems, handle business, feast, and enjoy festivities in castles. So castles served as social centers as well.

    The first castles were made from earth and wood, and they were likely to suffer from attacks by fire. Then wooden castles were gradually replaced by stone, which greatly increased the strength of these towers and walls. However, attackers could throw flaming objects into castles through the windows or burn the wooden doors. This led to moving the windows and entrances off of the ground floor and up to the first floor to make them more difficult to access.

    During the Middle Ages, attacks increased in regularity, so castle defenses were updated. Arrow-slits were added. They were small holes in the castle, which allowed defenders to fire without being hurt. Towers were built from which defenders could provide fire on both sides. The towers were connected to the castle by wooden bridges, so that if one tower fell, the rest of the castle was still easy to defend. A lot of rings of castle walls were constructed, so that even if attackers went past one wall, they would be caught on a killing ground between inner and outer walls. All of these increased the defense of castles.

    The end of castles can be attributed to gunpowder. During the 15th century, artillery, a kind of large guns, became powerful enough to break through stone walls. This greatly made the role of castles less effective. Though castles no longer serve their original purposes, remaining castles receive millions of visitors each year who wish to experience the situations of ancient times.

Work and the Young: Generation Jobless

    “YOUNG people ought not to be idle (闲置的) . It is very bad for them," said MargaretThatcher in 1984. She was right: there are few worse things that society can do to its young than to leave them ignored.

    Yet more young people are idle than ever. The International Labour Organization reports that 75m (m=million) young people globally are looking for a job. World Bank surveys suggest that 262m young people are economically inactive. The number of young people without a job is nearly as large as the population of America (311m).

Two factors play a big part. First, the long slowdown in the West has reduced demand for labour, and it is easier to put off hiring young people than it is to fire older workers. Second, inemerging economies population growth is the fastest in countries with disordered labour markets, such as India and Egypt.

    One possible way to settle this problem is to stimulate growth. That is easier said than done in a world suffering from debt, and is anyway a possible answer. The countries where the problem is worst (such as Spain and Egypt) suffered from high youth unemployment even when their economies were growing. Throughout the recession ( 经济不景气)，companies have continued to complain that they cannot find young people with the right skills. This underlines the importance of two other solutions: reforming labour markets and improving education.

    Youth unemployment is often at its worst in countries with inflexible labour markets. High taxes on hiring, strict rules about firing, high minimum wages: all these help force young people to the street corner. South Africa has some of the highest unemployment, in part because it has powerful trade unions and inflexible rules about hiring and firing. Many countries with high youth unemployment rate have high minimum wages and heavy taxes on labour. India has around 200 laws on work and pay.

    Across the OECD (经合组织) , people who left school at the earliest opportunity are twice as likely to be unemployed as university graduates. But it is unwise to conclude that governments should simply continue increasing the number of people who graduate from university. In both Britain and the United States many people with arts degrees are finding it impossible to get appropriate jobs. In North Africa university graduates are twice as likely to be unemployed as non-graduates.

    What matters is not just number of years of education people get, but its content. This means expanding the study of science and technology and closing the gap between the world of education and the world of work-for example by upgrading vocational education and by building closer relations between companies and schools. Germany, which has the second lowest level of youth unemployment in the rich world, owns long-history system of vocational schooling and apprenticeships (学徒制).

    The problem of youth unemployment has been getting worse for several years. But there are at last some reasons for hope. Governments are trying to address the mismatch between education and the labour market. Companies are beginning to take more responsibility for the young. The world has a real chance of introducing an education-and-training revolution worthy of the solution to the problem.

    What's it like to become a music star with millions of fans? These young artists know the feeling. Over the course of their short careers, they have attracted the attention of the biggest stars in the world and taken home prizes from major shows. For now they're just kids that everyone in music is watching. Check out the next generation of stars below.

    FIFTH HARMONY

    The 1990s was a brilliant period for girl groups. But after that few groups have been able to make much of an influence. This doesn't seem to bother Fifth Harmony, who landed the biggest hit of their career in 2016 with "Work from Home", a pop song that encourages everyone to ask for leave more often. When it climbed to No.4 on the Billboard Hot100, it was the first time that a girl group had entered the top 5 in the past ten years.

    LORDE

    It's been four years since the release of Born Heroine — the hot selling CD that made her a 16-year-old global sensation and the spokeswoman for a new generation of smart, strong-minded, creative female pop artists. She contributed to The Hunger Games soundtrack (插曲) in 2014, and for this time setting foot in Hollywood production also brought her more opportunities in her following career.

    TROYE SIVAN

    You might recognize the rising star Troye Sivan from YouTube, where he's been uploading videos since he was 12 and his channel already has millions of fans, or from the movies, where he played the role of young Wolverine in X-Men Origins: Wolverine.