职称英语考试真题
职称英语考试真题本文简介:2013年职称英语考试真题-理工类C级阅读判断第2部分:阅读判断(第16~22题,每题1分,共7分)下面的短文后列出了7个句子,请根据短文的内容对每个句子做出判断:如果该句提供的是正确信息,请选择A;如果该句提供的是错误信息,请选择B;如果该句的信息文中没有提及,请选择C。RadiocarbonDa
职称英语考试真题本文内容:
2013年职称英语考试真题-理工类C级阅读判断
第2部分:阅读判断(第16~22题,每题1分,共7分)
下面的短文后列出了7个句子,请根据短文的内容对每个句子做出判断:如果该句提供的是正确信息,请选择A;如果该句提供的是错误信息,请选择B;如果该句的信息文中没有提及,请选择C。
Radiocarbon
Dating
Nowadays
scientists
can
answer
many
questions
about
the
past
through
a
technique
called
radiocarbon
(放射性碳),or
carbon-14,dating.
One
key
to
understanding
how
and
by
something
happened
is
to
discover
when
it
happened.
Radiocarbon
dating
was
developed
in
the
late
1940s
by
physicist
Willard
F.
Libby
at
he
University
of
Chicago.
An
atom
of
ordinary
carbon,called
carbon-12,has
six
protons(中子)
and
six
neutrons
(质子)
in
its
nucleus.
Carbon-14,or
C-14,is
a
radioactive,unstable
form
of
carbon
that
has
two
extra
neutrons
(原子核).
It
returns
to
a
more
stable
form
of
carbon
through
a
process
called
decay
(衰减).
This
process
involves
the
loss
of
he
extra
neutrons
and
energy
from
the
nucleus.
In
Libby
s
radiocarbon
dating
technique,the
weak
radioactive
emissions
(放射)
from
his
decay
process
are
counted
by
instruments
such
as
a
radiation
detector
and
counter.
He
decay
rate
is
used
to
determine
the
proportion
of
C-14
atoms
in
the
sample
being
dated.
Carbon-14
is
produced
in
the
Earth
s
atmosphere
when
nitrogen
(氮)-14,or
N-14,interacts
with
cosmic
rays
(宇宙射线).
Scientists
believe
since
the
Earth
was
formed,the
mount
of
nitrogen
in
the
atmosphere
has
remained
constant.
Consequently,C-14
formation
is
thought
to
occur
at
a
constant
rate.
Now
the
ratio
of
C-14
to
other
carbon
toms
in
the
atmosphere
is
known.
Most
scientists
agree
that
this
ratio
is
useful
for
dating
items
back
to
at
least
50,000
years.
All
life
on
Earth
is
made
of
organic
molecules
(分子)
that
contain
carbon
atoms
coming
from
the
atmosphere.
So
all
living
things
have
about
the
same
ratio
of
C-14
atoms
to
other
carbon
atoms
in
their
tissues
(组织).
Once
an
organism
(有机体)
dies
it
tops
taking
in
carbon
in
any
form,and
the
C-14
already
present
begins
to
decay.
Over
time
the
amount
of
C-14
in
the
material
decreases,and
the
ratio
of
C-14
to
other
carbon
toms
goes
down.
In
terms
of
radiocarbon
dating,the
fewer
C-14
atoms
in
a
sample,the
older
that
sample
is.
16
Nowadays
many
scientists
depend
on
radiocarbon
for
dating
age-old
objects
ARight
B
Wrong
CNot
mentioned
17
The
radiocarbon
dating
technique
is
only
about
40
years
old
ARight
B
Wrong
CNot
mentioned
18
An
atom
of
ordinary
carbon
has
six
protons
and
eight
neutrons
ARight
B
Wrong
CNot
mentioned
19
Radar
is
used
to
determine
the
characteristics
of
radiocarbon.
ARight
B
Wrong
CNot
mentioned
20
Radiocarbon
is
reliable
in
dating
an
object
back
to
at
least
50,000
years.
ARight
B
Wrong
CNot
mentioned
21
When
an
organism
dies,the
C-14
in
it
begins
to
decay.
ARight
B
Wrong
CNot
mentioned
22
The
half-life
of
C-14
is
about
25,000
years.
ARight
B
Wrong
CNot
mentioned