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.

    Humans have been keeping animals as pets for tens of thousands of years, but Dr Jean-Loup Rault, an animal scientist at the University of Melbourne in Australia, believes new companions are coming: robot pets.

    “Technology is moving very fast,” Rault told ABC News, “The Tamagotchi in the early 1990s was really the first robotic pet, and now Sony and other big companies have improved them a lot.”

    This may not sit well with pet lovers. After all, who would choose a plastic toy over a lovely puppy? But Rault argues that the robotic kind has a lot going for it: “You don't have to feed it, you don't have to walk it, it won't make a mess in your house, and you can go on a holiday without feeling guilty.” The technology also benefits those who are allergic to pets, short on space, or fearful of real animals.

    It's not clear whether robot pets can replace real ones. But studies do suggest that we can bond with these smart machines. People give their cars names and kids give their toy animals life stories. It's the same with robots. When Sony stopped its repair service for its robot dog Aibo in March 2014, owners in Japan held funerals.

    As an animal welfare researcher, Rault is concerned about how robotic pets could affect our attitudes towards live animals. “If we become used to a robotic companion that doesn't need food, water or exercises, perhaps it will change how humans care about other living beings,” he said.

    So are dogs and cats a thing of the past, as Rault predicts? For those who grew up with living and breathing pets, the mechanical kind might not do. But for our next generation who are in constant touch with smart technology, a future in which lovely pets needn't have a heartbeat might not be a far-fetched dream.

    Chokwe Selassie, aged 13, is working hard to help drivers avoid potholes(坑洼). The eighth-grader was inspired to kick off his creation on a recent morning, when his mother was driving him to school. Their car was damaged as it went over a huge pothole in the middle of the street in their hometown of Jackson, Mississippi. He decided to do something about the pothole problem in his city. His solution: an app that warns drivers when there is a pothole ahead.

    Chokwe developed the app with his friends Rodriguez Ratliff and Emmanuel Brooks. When the app detects a pothole, it is highlighted in red. And if you get close to the pothole, your phone will warn you. Drivers can also use the app to report any potholes they meet, and to look for other routes they can take to avoid roads that have them.

    The app relies on current available information about the streets of Jackson. It works by using the city's 311 call system, and uses information already stored in a database. Through the call system, citizens dial 311 to report non-emergency problems, which include potholes. Chokwe and his friends determined that focusing on the 10 busiest streets in Jackson would give them a large enough sample size to test the prototype（原型）.

    Although the app isn't yet available for sale,Chokwe is already looking for ways to improve it. The prototype remains limited to 10 streets in Jackson, but he hopes to add more, so that it includes every street in the city. And then he wants to go even farther until it's nationwide.

    Women are friendly. But men are more competitive. Why? Researchers have found it's all down to the hormone oxytocin （荷尔蒙催生素）. Although known as the love hormone, it affects the sexes differently.

    "Women tend to be social in their behavior. They often share with others. But men lend to be competitive. They are trying to improve their social status," said Professor Ryan.

    Generally, people believe that the hormone oxytocin is let out in our body in various social situations and our body creates a large amount of it during positive social interactions （互动） such as falling in love or giving birth.

    But in a previous experiment Professor Ryan found that the hormone is also let out in our body during negative social interactions such as envy.

    Further researches showed that in men the hormone oxytocin improves the ability to recognize competitive relationships, but in women it raises the ability to recognize friendship.

    Professor Ryan's recent experiment used 62 men and women aged 20 to 37. Half of the participants（参与者）received oxytocin. The other half received placebo （安慰剂）.

    After a week, the two groups switched with participants. They went through the same procedure with the other material.

    Following each treatment, they were shown some video pictures with different social interactions. Then they were asked to analyze the relationships by answering some questions. The questions were about telling friendship from competition. And their answers should be based on gestures, body language and facial expressions.

    The results indicated that, after treatment with oxytocin, men's ability to correctly recognize competitive relationships improved, but in women it was the ability to correctly recognize friendship that got better.

    Professor Ryan thus concluded: "Our experiment proves that the hormone oxytocin can raise people's abilities to better distinguish different social interactions. And the behavior differences between men and women are caused by biological factors （因素） that are mainly hormonal. "

    The flowers are blooming and the birds are singing as Melinda sits in the rose garden of the nursing home. She is recalling old times as she waits for her family's arrival. The nursing home has been Melinda's new settlement ever since Thomas passed away a week ago. Thomas had fought a long and hard battle against lung cancer for three years. Unfortunately, he has broken the promise that he and Melinda had made: to be with each other for every birthday. Melinda knew this was unrealistic (不现实的) but agreed to the promise for Thomas's sake.

    "Thomas, you are completely a dreamer." Melinda shouted to Thomas as he dragged on about living on an island with his beautiful wife. That's what she loved about him most—he had a vivid imagination. They got married at age eighteen and began having children right away. Mary came within the year, followed by Thomas Benjamin II, Lilly-Ann, and Joseph “Little Joey” George. The family lived an exultant life filled with laughter and love.

    "Mom!" Lilly shouted, but it really sounded like a howl. Melinda had lost herself in thinking about the life she had shared with her late husband. Lilly pushed her down the long dark halls of the nursing home until they arrived at the recreational room.

When the doors opened, Melinda put her hand over her mouth and was completely speechless. The room was crowded with the people nearest and dearest to her and the warmth and love was felt instantly. The night went on; stories and cocktails were shared and everything was perfect.

    However, when Melinda caught a moment to herself she looked around at her family. With a smile on her face, she raised her Manhattan and called out for a toast. “This one is for you, Thomas, though you are not here.”

    John Blanchard stood up from the bench, straightened his Army uniform, and studied the crowd of people making their way through Grand Central Station. He looked for the girl whose heart he knew, but whose face he didn't, the girl with the rose.

    His interest in her had begun thirteen months before in a Florida library. Taking a book off the shelf he found himself intrigued, not with the words of the book, but with the notes penciled in the margin. The soft handwriting reflected a thoughtful soul and insightful mind. In the front of the book, he discovered the previous owner's name, Miss Hollis Maynell. With time and effort he located her address. She lived in New York City. He wrote her a letter introducing himself and inviting her to correspond. The next day he was shipped overseas for service in World War II.

    During the next year and one month the two grew to know each other through the mail. Each letter was a seed falling on a fertile heart. A romance was budding. Blanchard requested a photograph, but she refused. She felt that if he really cared, it wouldn't matter what she looked like.

    When the day finally came for him to return from Europe, they scheduled their first meeting -- 7:00 PM at the Grand Central Station in New York. "You'll recognize me," she wrote, "by the red rose I'll be wearing on my lapel." So at 7:00 he was in the station looking for a girl whose heart he loved, but whose face he'd never seen.

    I'll let Mr. Blanchard tell you what happened: A young woman was coming toward me, her figure long and slim. Her blonde hair lay back in curls from her delicate ears; her eyes were blue as flowers. Her lips and chin had a gentle firmness, and in her pale green suit she was like springtime come alive. I started toward her, entirely forgetting to notice that she was not wearing a rose. As I moved, a small, attractive smile curved her lips. "Going my way, sailor?" she murmured.

    Almost uncontrollably I made one step closer to her, and then I saw Hollis Maynell. She was standing almost directly behind the girl. A woman well past 40, she had graying hair tucked under a worn hat. She was more than plump, her thick-ankled feet thrust into low-heeled shoes. The girl in the green suit was walking quickly away. I felt as though I was split in two, so keen was my desire to follow her, and yet so deep was my longing for the woman whose spirit had truly companioned me and upheld my own.

    And there she stood. Her pale, plump face was gentle and sensible, her gray eyes had a warm and kindly twinkle. I did not hesitate. My fingers gripped the small worn blue leather copy of the book that was to identify me to her.

    This would not be love, but it would be something precious, something perhaps even better than love, a friendship for which I had been and must ever be grateful. I squared my shoulders and saluted and held out the book to the woman, even though while I spoke I felt choked by the bitterness of my disappointment. "I'm Lieutenant(中尉)John Blanchard, and you must be Miss Maynell. I am so glad you could meet me; may I take you to dinner?"

    The woman's face broadened into a tolerant smile. "I don't know what this is about, son," she answered, "but the young lady in the green suit who just went by, she begged me to wear this rose on my coat. And she said if you were to ask me out to dinner, I should go and tell you that she is waiting for you in the big restaurant across the street. She said it was some kind of test!"

    It's not difficult to understand and admire Miss Maynell's wisdom. The true nature of a heart is seen in its response to the unattractive. "Tell me whom you love," Houssaye wrote, "And I will tell you who you are."