Many children first learn the value of money by receiving an allowance. The purpose is to let children learn from experience at an age when financial mistakes are not very costly.

    The amount of money that parents give to their children to spend as they wish differs from family to family. Timing is another consideration. Some children get a weekly allowance. Others get a monthly allowance.

    In any case, parents should make clear what, if anything, the child is expected to pay for with the money.

    At first, young children may spend all of their allowance soon after they receive it. If they do this, they will learn the hard way that spending must be done within a budget. Parents are usually advised not to offer more money until the next allowance. The object is to show young people that a budget demands choices between spending and saving. Older children may be responsible enough to save money for larger costs, like clothing or electronics.

    Allowances give children a chance to experience the things they can do with money. They can share it in the form of gifts or giving to a good cause. They can spend it by buying things they want. Or they can save and maybe even invest (投资) it.

    Saving helps children understand that costly goals require sacrifice: you have to cut costs and plan for the future. Requiring children to save part of their allowance can also open the door to future saving and investing. Many banks offer services to help children and teenagers learn about personal finance. A savings account is an excellent way to learn about the power of compound interest (利息). That may not seem like a lot. But over time it adds up.

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    Camping -Yellowstone National Park

    Camping rules

    Camping or parking in picnic areas, picnic grounds，or any place other than a designated (指定的) campground is not permitted. However, camping is often allowed in neighboring communities and forests outside the park.

    Camping is limited to 14 days between June 15 and September 15 and to 30 days the rest of the year. Check - out time for all campgrounds is 10:00 am.

    Quiet hours

    Camping in Yellowstone is a special experience. Each visitor deserves the opportunity to hear the birds, wildlife, and streams in this beautiful environment. Respect the rights of other campers and obey the law by keeping quiet from 8:00 pm to 8:00 am. No noises will be allowed during this time.

    Golden Age/ Golden Access discounts

    Holders of Golden Age and Golden Access permits will be given about 50% discounts on camping fees.

    Croup camping

    Group camping are permitted at Madison, Grant and Bridge Bay campgrounds from late May till the closing date for large organized groups with a designated leader such as youth groups or educational groups. The fees change per night, depending on the size of the group. Advance reservations (预定) are required and can be made by calling (866) 439 -7375.

    Nowadays wind is useful. Think about the different ways that people use the wind. You can use it to fly a kite or to sail a boat. Wind is one of our cleanest and richest power sources, as well as one of the oldest. Evidence shows that windmills began to be used in ancient Iran back in the seventh century BC. They were first introduced to Europe during the 1100s, when armies returned from the Middle East with knowledge of using wind power.

    For many centuries, people used windmills to grind wheat into flour or pump water from deep underground. When electricity was discovered in the late 1800s, people living in remote areas began to use them to produce electricity. This allowed them to have electric lights and radio. However, by the 1940s, when electricity was available to people in almost all areas of the United States, windmills were rarely used.

    During the 1970s, people started becoming concerned about the pollution that is created when coal and gas are burned to produce electricity. People also realized that the supply of coal and gas would not last forever. Then, wind was rediscovered, though it means higher costs. Today, there is a global movement to supply more and more of our electricity through the use of wind.

    It has taken an extremely long time－161 years－but the National Portrait Gallery finally has the Duke(公爵)of Wellington in its collection after a fundraising campaign reached its ￡1. 3m target.

    The gallery announced on Thursday that it had acquired Sir Thomas Lawrence's unfinished final painting of a man regarded as Britain's greatest soldier after a successful appeal.

    Nicholas Cullinan, the gallery's director, said the NPG had been looking for a suitable painting of the Duke of Wellington since the gallery was founded in 1856.

    He called it "a remarkable painting", while Lucy Peltz, the gallery's senior manager of 18th­century paintings, said the work was "an inspiring and powerful image of one of the most influential men of the 18th and 19th centuries".

    The NPG announced last November that it needed to raise ￡300,000, the final piece of a funding jigsaw(拼图). The Art Fund had already contributed ￡350,000 and the appeal reached its target thanks to ￡200,000 from the G&K Boyes charitable trust and ￡180,000 from the National Heritage Memorial Fund. A further ￡570,000 came from a public appeal and the gallery's own funds.

    It was painted in 1829 when Wellington was prime minister, however, Lawrence died in 1830 leaving the portrait unfinished. The gallery believes it is a more attractive work because of that, with the viewer focusing more on the man himself rather than any clothes of power.

    Dan Snow, the historian and broadcaster, said Wellington was a "Titanic figure" in British history, the only field greatest prime minister, a man of genius on and off the battlefield. He added:" This arresting portrait must sit in the national collection and now, following an outpouring of donation, it will do. The artist has caught the Duke's legendary features. Among his many contributions to British life he formed the culture of unbending spirit in the face of difficulty."

    The painting was lent to the NPG in 2015 for an exhibition marking the Battle of Waterloo.

    Humans and elephants don't always get along. In Africa and Asia, elephants damage equipment, farmers' crops, and natural habitat for other species. If an elephant becomes a problem, humans may kill it. So local people and animal protectionists are trying to find better ways to keep elephants away from sensitive places. Now, researchers think they have a good tool to prevent elephants: honeybee pheromones (信息素).

    “Elephants dislike being stung(叮咬) in the trunk, because it's an extremely sensitive organ. Imagine being stung in your nose by a bee, and multiply that a few thousand times.” said Mark Wright, a professor at the University of Hawaii.

    Kenyan farmers have long known that if they hang live beehives (蜂箱) around their farms, they will drive elephants away. The problem is how to manage hundreds of thousands of hives, if you have a huge area to protect. And then the idea came up to look at the alarm pheromones, which are chemicals that the bees release to launch an attack on something that's damaging the hive.

    So the researchers tested out an artificial mixture of chemicals that imitates (模仿) honey bees' alarm pheromones. The researchers hung white socks treated with the artificial mixture as well as untreated control socks around an elephant watering hole, and then observed the animals' behavior. “Elephants are really curious creatures. They'll walk along and see something like a sock hanging on a branch. If it's not treated with the alarm pheromones, they'll pick it up, throw it around, and try to taste it, things like that. And in the case of the treated ones, they would show immediate signs of unease or uncertainty, and they'd eventually back off from them.”

    In order to avoid the elephants more effectively, the researchers plan to make the pheromone mixture purer. That way, elephants will stay far away from wherever they should not be going-and both elephants and humans can coexist a bit more peacefully.

    From the earliest times, man has been interested in art. People have often worked together to collect and save the world's art treasures.

    Fine art treasures from many countries are kept in an art museum called the Louvre(卢浮宫)in Paris, France. The works of art have been collected by the people of France over many centuries.

    The Louvre has not always been a museum. The first building was a fort(炮台). In 1190, it was the king's castle with high walls and a round tower. It had a moat to keep out his enemies.

    Over the years, the number of buildings around the castle grew. By 1350, the castle was no longer needed as a fort. The Louvre became a palace home for French kings and queens.

    During times of peace, new treasures were brought in. During days of war, many treasures were stolen, and the buildings were damaged.

    When Francis Ⅰ became the king of France in 1515, he brought in artists from many countries. One of the artists was Leonardo da Vinci from Italy. Da Vinci's Mona Lisa is the best known painting in the museum today.

    In 1793, the Louvre became a public museum, just as it is now. It is a place where art treasures have been saved for everyone to enjoy.