The half-life of C-14 is about 25，000 years.

试卷相关题目

• 1When an organism dies， the C-14 in it begins to decay.

  A.Right

  B.Wrong

  C.Not mentioned

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• 2Radiocarbon is reliable in dating an object back to at least 50，000 years.

  A.Right

  B.Wrong

  C.Not mentioned

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• 3Radar is used to determine the characteristics of radiocarbon.

  A.Right

  B.Wrong

  C.Not mentioned

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• 4An atom of ordinary carbon has six protons and eight neutrons

  A.Right

  B.Wrong

  C.Not mentioned

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• 5The radiocarbon dating technique is only about 40 years old

  A.Right

  B.Wrong

  C.Not mentioned

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• 6On a clear night， people can see

  A.150 stars.

  B.hundreds of stars.

  C.one thousand stars.

  D.more than 14，000 stars.

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• 7Light pollution occurs when

  A.artificial lights illuminate the night sky.

  B.the moon lights up the night sky.

  C.too many stars are visible in the night sky

  D.streetlights are turned off.

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• 8Nowadays even suburbs are becoming unsuitable for scientists to do their jobs because

  A.the night sky there is too dark.

  B.the once dark areas are also polluted by lights.

  C.these areas are not polluted by chemicals.

  D.these areas are less developed.

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• 9How does light pollution affect wildlife？

  A.Animals may go off course.

  B.It helps migrating birds find their homes.

  C.Animals are afraid to go out after sunset.

  D.It helps birds fall asleep.

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• 10The title “Light Night， Dark Stars” means

  A.the night sky is brightly lit up and stars are black.

  B.lights appear at night and stars are seen in the dark.

  C.city lights at night illuminate stars in the sky.

  D.city lights illuminate the night sky， making stars invisible

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