Scientists have always believed that snails are not able to find their way home. But Briton Ruth Brooks, a retired teacher, has found that it is not true.

    Brooks began an experiment on snails after she got mad with the snails in her garden.

    The snails had eaten her vegetables. She didn't want to kill them, so she took them to another place. But she found they always seemed to come back.

    Brooks did an experiment. She marked the snails in her garden with nail polish(指甲油).

    She placed the snails in the area around her home and made notes of their movements.

    She found that snails have a strong homing instinct (本能); the longest returning snail traveled back 90 meters. Brooks has been named Britain's best amateur (业余的) scientist after her work won the BBC Radio 4 project, So You Want To Be A Scientist.

    She said, "I've always wanted to know whether the snails that eat my plants just come back when I move them, and if they do, what is their homing distance?

    "I would say on the evidence (证据) that it would be safe to take your snails away beyond 100m or even further. If you put them somewhere nice with some food, you can be almost certain that they won't come back."

Canada Day

    Since 1982, July 1st has been officially known as Canada Day. Canadians of all ages take part in this festival across the country.

    Canada Day is the year's biggest national party. In many towns and cities, the government organizes a lot of events, often outdoors. These include parades（游行）, concerts, festivals,

    firework displays and ceremonies for new Canadian citizens（公民）.The celebrations often have apatrioticmood. Canada's national flag, a symbol for Canada Day, can be seen everywhere and a lot of people paint their faces red and white, which are Canada's national colors. The celebrations in Ottawa, Canada's capital city, are especially grand and exciting.

    In the province of Quebec, many home rentals（租赁）start on July 1st and last for exactly one year, and many people in Quebec spend Canada Day moving from one house to another. So in Quebec, Canada Day is also known as Moving Day.

    Many organizations, businesses and stores are closed this day. Only some bookstores, hospitals and gas stations may be open. Post offices are closed, too. As Canada Day falls in the Canadian summer holiday period, all schools are closed as well. In some areas, special services are provided for large events. The concerts, parades and festivals may cause some traffic jams.

通过对《多彩的光》学习，以下物理现象中符合客观事实的是（　　）