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| 文章出处：学生大考试站 发布时间：2005-10-12 |
when
c. many years ago that
d. for many years since
48. ________ when everyone has to think for himself.
a. There comes a time
b. Here comes a time
c. There goes a time
d. A time comes here
49. Some speculators were _______ cash and so they sold their shares at any price.
a. badly needed
b. badly need for
c. in badly need of
d. badly in need of
50. My sister can't cook; ______.
a. either can my brothers
b. nor my brother can
c. neither can't my brother
d. my brother can't either
Part IV Error Correction
Directions: This part consists of a short passage. In this passage, there are altogether
10mistakes, one in each numbered line. You may have to add a word, cross out a
word, or change a word.
In 1960 an American physicist built an interesting new apparatus to produce a very
strong beam of light. This new light was named after "laser".
51. ______
The principle of the laser is that the atoms of a crystal like the ruby crystal can be
excited by strong light and can then store this light, amplify it and emit an immensely
powerful beam. This light is particularly powerful when it travels in coherent waves,
that is, waves which are all the same length and
52. _____
which move in step. For this reason, too, this light consists of only one colour, and
not of many colours unlike sunlight.
53. _____
Light of this strength can be very useful and has already found much different
applications in science. One important use of laser is to measure distance.
54. _____
The astronauts on one Apollo mission set up a reflector on the moon to "catch"
laser beams projected from the earth and to return them to our planet. By measuring
the time the beam takes to go to the moon and comes back, scientists
55. _____
can add the precise distance.
56. _____
Other use of lasers is to measure time. The fact that their pulses can be
57. ____
used to divide a single one second into very small parts. I
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