Most birds produce short, simple calls, but songbirds also have the ability of many complex vocal (发声的) patterns that help them attract mates, defend territory (领地), and strengthen their social bonds. Each songbird species has its own unique song patterns, some with characteristic regional dialects. Experienced listeners can even distinguish individual birds by their unique songs.

    A lot of what scientists know about bird song comes from studying zebra finches. A baby male zebra finch typically learns to sing from its father or other males, starting while it's still a baby bird in the nest. First comes the sensory learning stage, when the baby finch hears the songs sung around it and commits them to memory. The bird starts to vocalize during the motor learning stage, practicing until it can match the song it memorized. As the bird learns, hearing the tutor's song over and over again is helpful — up to a point. If it hears the song too many times, the imitation (模仿) becomes worse -- and the source matters. If the song is played through a loudspeaker, he can't pick it up as easily. But hide the same loudspeaker inside a toy painted to look like a zebra finch, and his learning improves.

    What if the baby never hears another zebra finch's song? Interestingly enough, it'll sing anyway. Isolated finches still produce what are called innate songs or isolate songs. A specific tune might be taught, but the instinct to sing seems to exist in a songbird's brain. Innate songs sound different from the “cultured” songs learned from other finches - at first. If isolate zebra finches start a new colony, the young birds pick up the isolate song from their fathers. But the song changes from generation to generation. And after a few generations, the melody actually starts to resemble the cultured songs sung by zebra finches in the wild.

    Beijing residents could be rewarded with up to 500,000 yuan if they can provide useful information on spies or related activities, according to a government policy that took effect on Monday.

    Under the policy, informants will be offered rewards ranging, from 10,000 yuan to 500,000 yuan, depending on how useful the information is, according to the policy issued by the National Security Bureau(安全局) of Beijing. Informants can pass information to authorities by calling a hotline, sending letters or visiting the bureau.

    Informants' privacy and information about spy-related messages will not be disclosed, while information providers can ask authorities for protection if they or their relatives are in danger due to the act of informing, according to the policy.

    However, informants will face punishments if they slander (诽谤) others on purpose or invent and spread false information, the policy states clearly.

    The bureau said that China is witnessing rapid increases in international exchanges and the number of people entering or exiting the country each year. "Meanwhile, overseas espionage agencies(间谍机构)and other unfriendly forces have also strengthened their disruptive(破坏的) activities in China, including political, economical and military information." it said.

    Some Chinese individuals have also betrayed the nation to benefit their private interests, which offers overseas espionage agencies opportunities, the bureau said, adding that Beijing is the primary location for such activities. Therefore, it's necessary to take new measures in anti-espionage investigation, and to encourage the participation of the general public.

    One of the most recent cases made public occurred in the eastern province of Jiangsu in January. Two residents in Lianyungang city, surnamed Zhang and Wan, called the national security authorities after they found a device with instructions in foreign languages while fishing in the Yellow Sea. The device was later found to be spying equipment made and used by overseas agencies to collect data, according to an official release.

    China has strengthened legislation(立法) on State security in recent years. Facing a more complex State security situation, in 2014, the Standing Committee of the National People's Congress adopted the Counterespionage Law.

    Albert Einsein said," Only a life lived for others is worth living."

How does this job offer sound? You'll need to be available on short notice，including late at night and on weekends. You could be asked to do anything from helping at community events to responding to life-threatening emergencies (sometimes putting your own safety at risk). This job also involves a lot of regular training. Oh, and you won't be paid for any of this. Would you take the job?

    This job might not necessarily appeal to everyone, but if this sounds like an opportunity you'd eagerly accept，then you'd fit right in with Western Australia's 26,000 emergency service volunteers. The emergency services aren't the only industry benefiting from volunteers. Across both Australia and America, between a quarter and half of the population volunteer each year in areas including education, sports, health, religion, and social services.

    What motivates people to volunteer? Yes, volunteers don't get paid. But it doesn't mean people don't get benefits from volunteering. Indeed, research shows there are significant mental health benefits coming with volunteering. It can be a means to make new friends, build new skills or try things out of your comfort zone. It can also be a means to help loved ones. A case is someone close to me who recently lost her husband to a disease. When her husband was admitted to a nursing facility, she decided to volunteer for the patient advocacy committee. She found great support and felt she could make a difference in the lives of the patients. After her husband's passing, she decided to continue volunteering for the committee not only as a way to show gratitude for the great care her husband received but also because she made friends there. She found a way to put her career skills to use for the common good and keep active after retirement.

    There are countless ways to volunteer. No matter how you do it, it is definitely worth every minute you put into it.

    Failure is probably the most exhausting experience a person ever has. There is nothing more tiring than not succeeding.

    We experience this tiredness in two ways: as start-up fatigue(疲惫) and performance fatigue. In the former case, we keep putting off a task because it has either too boring or too difficult. And the longer we delay it, the more tired we feel.

    Such start-up fatigue is very real, even if not actually physical, not something in our muscles and bones. The solution is obvious though perhaps not easy to apply: always handle the most difficult job first.

    Years ago, I was asked to write 102 essays on the great ideas of some famous authors. Applying my own rule, I determined to write them in alphabetical(按字母顺序), never letting myself leave out a tough idea. And I always started the day's work with the difficult task of essay-writing. Experience proved that the rule works.

    Performance fatigue is more difficult to handle. Though willing to get started, we cannot seem to do the job right. Its difficulties appear so great that, however hard we work, we fail again and again. In such a situation, I work as hard as I can-then let the unconscious take over.

    When planning Encyclopaedia Britannica (《大英百科全书》), I had to create a table of contents based on the topics of its articles. Nothing like this had ever been done before, and day after dat I kept coming up with solutions, but none of them worked. My fatigue became almost unbearable.

    One day, mentally exhausted, I wrote down all the reasons why this problem could not be solved. I tried to convince myself that the trouble was with the problem itself, not with me. Relived, I sat back in an easy chair and fell asleep.

    An hour later, I woke up suddenly with the solution clearly in mind. In the weeks that followed, the solution which had come up in my unconscious mind provided correct at every step. Though I worked as hard as before, I felt no fatigue. Success was now as exciting as failure had been depressing.

    Human beings, I believe must try to succeed. Success, then, means never feeling tired.

What gives your life meaning? It is an important and natural practical question that we all ask ourselves at times. It circles around the notion of having a purpose and a reason to wake up and move forward in our lives. {#blank#}1{#/blank#} Is it time to bring it back on track? Here's how to get started.

Treat your depression

Your depression empties your energy and damages your motivation. {#blank#}2{#/blank#} Therefore, the key here is taking action no matter what you start with: tackling the depression directly through taking medicines or consulting doctors to get you moving forward. What the action is matters less than taking action itself.

Get out of your head into your emotion

If you are heavily driven by what you should do, you need to start rewiring your brain to use your emotions as information. {#blank#}3{#/blank#} Once you notice them, do something concrete with them - again, act. That is how you learn to trust your emotions and use them to guide you, and how you rewire your brain.

Explore, experiment

You can't figure out your sense of purpose by sitting on the couch and thinking it over. {#blank#}4{#/blank#} You also need to focus on doing different experiments with being bold, and taking acceptable risks.

The path to discovering or reigniting your sense of purpose is not about making a new decision but focusing on the process that leads to that decision. {#blank#}5{#/blank#}

A. Hence, your emotions are your source of passion, desire, and energy.

B. It may be caused by physical or emotional limitations that take away joy.

C. However, for many, that sense of purpose has been absent for long stretches.

D. Without them, you don't make the changes that can pull you out of the depression.

E. Instead, you need to explore, try things and see what sticks, what works, what doesn't.

F. Start by focusing on those slightest feelings telling you what you want and don't want.

G. Therefore, you need to clear away obstacles that keep you from acting and moving forward.

China is known as the home of tea.It is said that Shennong discovered tea around 2700 BCE.At first,tea leaves {#blank#}1{#/blank#}(chew).During the Tang Dynasty,{#blank#}2{#/blank#}(advance) were made in the processing of tea.The leaves were steamed,oxidized(氧化) and pounded into the cake form.This made tea easier {#blank#}3{#/blank#}(transport) and more pleasing to the tongue. 

The earliest batch(批次) of tea is often ready to be picked before Qingming.This precious small output of tea,widely {#blank#}4{#/blank#}(seek) after for its outstanding quality,is called Mingqian tea.The seasonal tea is known {#blank#}5{#/blank#} its tender leaves and fresh flavor.They have {#blank#}6{#/blank#} better favor than theater batches which can be grown overnight. 

East China's Zhejiang Province is acknowledged as a major producer of tea.In spring,local hillsides {#blank#}7{#/blank#}(fill) with tea workers sowing seeds on their land.In the peak seasons,many tourists flood to witness the beautiful scenery of tea farms for {#blank#}8{#/blank#}(they),while enjoying a cup of tea. 

There are many ways you can experience tea culture in China.You can visit a tea plantation in Hangzhou or elsewhere to learn {#blank#}9{#/blank#} tea is grown and harvested.You can sit inside a {#blank#}10{#/blank#}(tradition) teahouse and take in the classical atmosphere as you drink tea.