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.

    As kids, my friends and I spent a lot of time out in the woods,"The woods" was our part-time address, destination,purpose,and excuse.If I went to a friend's house and found him not at home,his mother might say, "Oh,he's out in the woods,"with a tone of airy acceptance.It's similar to the tone people sometimes use nowadays to tell me that someone I'm looking for is on the golf course or at the gym,or even "away from his desk."For us ten-year-olds,"being out in the woods" was just an excuse to do whatever we feel like for a while.

    We sometimes told ourselves that what we were doing in the woods was exploring.Exploring was a more popular idea back then than it is today.History seemed to be mostly about explorers.Our explorations,though,seemed to have less system than the historic kind: something usually came up along the way.Say we stayed in the woods, throwing rocks,shooting frogs,picking blackberries,digging in what we were briefly persuaded was an Italian burial mound.

    Often we got "lost" and had to climb a tree to find out where we were.If you read a story in which someone does that successfully,be skeptical: the topmost branches are usually too skinny to hold weight,and we could never climb high enough to see anything except other trees.There were four or five trees that we visited regularly—tall beeches,easy to climb and comfortable to sit in.

    It was in a tree,too,that our days of fooling around in the woods came to an end.By then some of us had reached seventh grade and had begun the rough ride of adolescence.In March,the month when we usually took to the woods again after winter,two friends and I set out to go exploring.We climbed a tree,and all of a sudden it occurred to all three of us at the same time that we really were rather big to be up in a tree.Soon there would be the spring dances on Friday evenings in the high school cafeteria.

    ARNOLD Schwarzenegger is back, once again taking on his iconic killer robot role, the T-800, in August's new movie Terminator Genisys. While the T-800 model—even if it can be evil—has a fond place in moviegoers' hearts, the reality of autonomous machines is no joke, according to scientists.

    Autonomous weapons use artificial intelligence (AI) to choose targets without human help. They were described as “the third revolution in warfare, after gunpowder and nuclear arms” in an open letter signed by over 1,000 important technology figures in July. The list included British scientist Stephen Hawking and Apple co-founder Steve Wozniak. They asked governments around the world to ban autonomous weapons, warning that killer robots could start ethnic cleansings and an arms race.

     “They will look like tanks. They will look like battleships. They will look like jet fighters,” UK robotics professor Noel Sharkey told CNET, a leading technology website.

    But unlike these machines, which require a human hand in their action, so-called “killer robots” would have some decision-making abilities and the ability to act on their own.

     “If any major military power pushes ahead with AI weapon development, a global arms race is almost inevitable,” said the letter released at the 2015 International Joint Conference on Artificial Intelligence in Buenos Aires, Argentina.

    The idea of an automated killing machine was made famous by Schwarzenegger's first Terminator movie in 1984. While no red-eyed robots have been sent after human beings, the idea of AI being used as a weapon has gotten much more likely in the years ever since. The US military is already developing autonomous flying vehicles that can carry out all the steps of a strike mission without a human controlling them, according to a May report in Nature magazine.

    Scientists have even painted a destructive picture of autonomous weapons falling into the hands of terrorists or warlords hoping to carry out ethnic cleansings.

     “The development of full artificial intelligence could lead to the end of the human race,” Hawking said to the BBC in 2016.

Authorities are gradually waking up to the risk of robot wars. Last May, for the first time, the United Nations brought governments together to begin talks on autonomous weapons systems.

    Still, a ban on autonomous weapons is “easier said than done”, commented The Guardian. The dual (双重的) uses of the AI technology—for harm and for good—is difficult to manage. This is because the exact same technology can be used in a wide range of ways, the paper said.

    Today's post is almost about signs in English. You will see signs on the road while driving or when walking down a street. Now let's take a closer look at the signs in the picture below, so you can fully understand what they mean in case you come across one of them.

    Starting with the top row, we have a:

    Yield sign—This sign indicates (标示) that you need to slow down ,but you may not have to come to a full stop.

    Crosswalk—This is a sign that indicates people have the right of way to cross the street, so cars have to stop when they see a person waiting next to one of these signs.

    Second row:

    Do not enter—This sign indicates you are not allowed to enter a road at that point.

    Buckle up(系好安全带)!— There are often signs on roads in the United States reminding people that wearing seat belts(安全带) is mandatory (强制的) (seat belt laws differ depending on what state you are in ,but all US states have seat belt laws).

    Third row:

    Be alert (警惕的) for bears—This is another sign that is used to indicate to drivers and pedestrians (行人) that they should be alert for wildlife in the area.

Playground—This is the sign used to alert drivers that there is a playground nearby, so it is a good idea to slow down and watch for children.

    Travelling to China is like travelling to another world. Its many famous beautiful places will make you lose yourself in them. However, it is usually not enough for a traveller only to visit these nice places. If you have time to see the local people, talk with them and even have dinner with a local family, it would be a wonderful experience, to know more about the local people's life style at home in China.

    New Hope Travel Agency will arrange (安排) a family visit to Xi'an, an ancient historic city in China. We especially have chosen typical local families to host this activity in which you can see the true living style of Chinese people. Most of the hosts retired (退休) at home, so they are happy to see visitors from different countries to come to their homes.

    Not only can we arrange to visit the local family but we can arrange to taste the true home cooked dishes. Our tour guide will ask you for advice about the food you want to eat. Just enjoy the locally cooked dishes. It'll be quite a different and exciting experience.

    Our agency also provides a good opportunity for you to learn to cook Chinese food. We have a general cooking class in the local family. If you'd like to learn to cook one or two Chinese dishes, please go to our Chinese Food Cooking Class to choose your favorite dishes.

    Don't wait. Welcome to China.

     Aspirin has long been praised as a wonder drug. An aspirin a day keeps the doctor away. Many Americans have been taking one aspirin a day, believing it would protect them from a heart attack a stroke(中风), and even a cancer. But several recent studies have thrown this into question. Daily use of aspirin can have serious side effects(副作用).

    One study followed more than 19,000 healthy people aged 65 and older. They were required to take either 100 mg of aspirin (a little more than the 81 mg dose that most people take) or a placebo(无效对照剂) every day for about years, Not only did people in the aspirin group not lower their risk of heart disease, or disability but they were also more likely to suffer from bleeding into the brain or stomach. And they were more likely to die because of an increased risk of giving in to cancer, Similarly, an experiment of more than 12. 500 people aged 55 and older who have a cardiovascular (心血管的)risk found no benefit to taking aspirin daily. In study of more than 15,000 people with diabetes(糖尿病), a daily aspirin did prevent heart attacks and strokes, but it also caused serious bleeding.

    Although some earlier research has proved that aspirin can help people who have already had or are at high risk for heart attacks or strokes, the drug's value is not so clear for people, especially older people,

    The bottom line is this: Be smart and be safe. You should not take daily low-dose aspirin without talking to a doctor if you.

    ● Are over the age of 70

    ● Drink wine regularly

    ●Are on any simple medical operations