Carbon dating can be used to estimate the age of any organic natural material; it has been used successfully in archeology to determine the age of ancient artifacts or fossils as well as in a variety of other fields. The principle underlying the use of carbon dating is that carbon is a part of all living things on Earth. Since a radioactive substance such as carbon-14 has a known half-life, the amount of carbon-14 remaining in an object can be used to date that object.

Carbon-14 has a half-life of 5,570 years, which means that after that number of years, half of the carbon- 14 atoms have decayed into nitrogen-14. It is the ratio of carbon-14 in that substance that indicates the age of the substance. If, for example, in a particular sample the amount of carbon- 14 is roughly equivalent to the amount of nitrogen-14, this indicates that around half of the carbon- 14 has decayed into nitrogen-14, and the sample is approximately 5,570 years old.

Carbon dating cannot be used effectively in dating objects that are older than 80,000 years. When objects are that old, much of the carbon-14 has already decayed into nitrogen-14, and the molecule amount that is left doesn’t provide a reliable measurement of age. In the case of older objects, other age-dating methods are available, methods which use radioactive atoms with longer half-lives than carbon has.

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions

This passage is mainly about ............

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• According to the passage, one function of the memory unit is ...............

• Why is noise difficult to measure?

• Which of the following is NOT true?

ZUNIA12

• This passage would probably be assigned reading in which of the following courses?

• According to the passage, all of the following are true about tidal waves EXCEPT that _____ .

• The word “tedious” in the last paragraph mostly means     .

• According to the passage, which of the following is NOT true about the tradition of tooth giving in the West?

• The public expects the following three services in handling and delivery of mail except ............

• The phrase "All in all "in the passage  is closest in meaning to .............

• The changes in the American home mentioned in this passage may ...........

• The word “woo” is closest in meaning to __________

• The word “exotic" in paragraph two is closest in meaning to ________.

• The word “it” in paragraph 1 refers to ____________.

• The word “sensational” is closest in meaning to .............

• What does the passage mainly discuss?

• The passage states that one solution to time management problem is to ..............

• It can be inferred from the passage that limestone deposits serve as the basis of ...........

• Animals found desert living possible only _____

• It can be inferred from the passage that the Puritans who traveled to the Massachusetts colony were ............

• The author indicates that the ruby-throated hummingbird is found _______.