TRIK JITU MENGERJAKAN SOAL TOEFL,WRITTEN EXPRESSION DAN PEMBAHASANNYA
TRIK JITU MENGERJAKAN SOAL TOEFL (READING)
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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 Eath.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.
Carcon-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 to nitrogen-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 minuscule amount that is left does not 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.
1.This passage is mainly about
a.the differences between arbon-14 and nitrogen-14
b.one method of dating old objects
c.archeology and the study of ancient artifacts
d.various uses for carbon
2.The word"estimate"in line 1 is closest in meaning to
a.understand
b.hide
c.rate
d.approximate
3.The pronoun "it"in line 1 refers to
a.carbon dating
b.the age
c.any organic natural material
d.archeology
4.Which of the following is NOT true about carbon-14?
a.It is radioactive
b.Its half-life is more than 5,000 years.
c.It and nitrogen always exist in equal amounts in any substance.
d.It can decay ino nitrogen-14
5.The word"underlying"in line 3 could best be replaed by
a.below
b.requiring
c.being studied through
d.serving as a basis for
6.It can be inferred from the passage that if an item contains more arbon-14 than nitrogen-14,then the item is
a.too old to be age-dated with carbon-14
b.not as much as 5,570 years old
c.too radioactive to be used by archeologists
d.more than 5,570 years old
7.The word"roughly"in line 9 could best be replaced by
a.harshly
b.precisely
c.coarsely
d.approximately
8.The expression"is left"in line 13 could best be replaced by
a.remains
b.has turned
c.changes
d.is gone
9.It is implied in the passage that
a.carbon dating could not be used on an item containing nitrogen
b.fossils cannot be age-dated using carbon-14
c.carbon-14 does not have the longest known half-life
d.carbon dating has no known uses outside of archeology
10.The paragraph following the passage most probably discusses
a.how carbon14 decays into nitrogen-1
b.various other age-dating methods
c.why arbon-14 has such a long half-life
d.what substances are part of all living things
referenece:
LONGMAN PREPARATION COURSE FOR THE TOEFL TEST
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