Unit 9

If you stand a short distance away from a high wall and shout, your voice sometimes comes back to you as an echo. This happens because the    1    waves are reflected    2    the wall. This is the principle of radar,    3    instead of sound it is radio waves which are reflected. This   4    was made a few years before the last war,   5    radio waves from a transmitting station    6    reflected back from a distant aeroplane.

It was realized    7    an apparatus could be devised to send out radio waves    8    and record the   9    from any approaching aeroplanes, it would be a wonderful method of defense    10    war.

Scientists    11    solving the problem and radar was    12   . An apparatus was made which sent out waves in pulses, and the presence of a distant aeroplane was shown on the screen of a cathode(陰極) ray tube, (this is    13    we have in a television set).    14    this way radar stations could detect the approach of enemy aircraft.

After the war radar was put to peaceful uses. It is now installed at airports to    15    aeroplanes down safely in fog. It is fitted to ships so that they are warned    16    obstructions ahead,   17    icebergs. It guides ships into port. It provides aeroplanes and ships    18    a magic eye, with    19    they can see    20    into the distance, in the dark or in fog.

1. A) voice             B) sound               C) shout                D) echo

2. A) off                B) on                    C) in                     D) against

3. A) so                 B) on                    C) but                   D) as

4. A) found            B) discover            C) knowledge        D) discovery

5. A) when            B) as                     C) until                  D) before

6. A) was                     B) were                 C) is                            D) are

7. A) if that            B) if when             C) that if               D) when if

8. A) all time          B) every time         C) any time            D) all the time

9. A) echoes          B) voices               C) sounds              D) waves

10. A) on               B) in                     C) at                            D) off

11. A) set off         B) set aside            C) set up               D) set about

12. A) found          B) seen                  C) made                D) invented

13. A) what           B) that                   C) which               D) that

14. A) On                  B) Upon                C) In                     D) Along

15. A) tell              B) guide                C) make                D) warn

16. A) from           B) of                     C) to                     D) in

17. A) so on           B) so that                     C) such as             D) as if

18. A) with            B) of                     C) for                   D) in

19. A) which          B) that                   C) this                   D) what

20. A) away           B) along                C) off                   D) far

Unit 10

Nature has a perfect system for recycling water. Water is used again and again. It falls as rain.   1    it goes to one of three places. It might seep slowly through the soil    2    it soaks through into the natural reservoirs   3   . It might disappear into the air by    4    quickly. It might    5    into streams to rivers and to the oceans.

There is a problem    6    this recycling system. It is a balance that can be easily    7    by people. Nature’s recycling system can work well    8    people work with the system—not    9    it. Some ways that people    10   with nature are easy    11   . Dirty sewage water from homes and factories must not    12    with drinking water. People would get sick from drinking dirty water.

   13    other ways that people hinder nature. Some of these ways are not so easy to understand.   14   , a marshy bog(沼澤) may not be good for everything, but it    15    an important purpose. The soft, wet soil of a bog    16    water to reach the underground reservoirs. What happens to the balance of nature if the bog is filled in? Many housing development projects have been built    17    marshes once were. The    18   of the houses are likely to have problems. They are likely to    19    water, to flood in    20    seasons. Huge storm sewers are built to carry away with the water from wet areas. These huge pipes prevent wet basements in the houses of the community.

1. A) Therefore             B) Then                               C) Consequently     D) Nevertheless

2. A) because                B) if                                    C) after                 D) as

3. A) in underground      B) below underground          C) underground      D) undergroundly

4. A) evaporating    B) being evaporating    C) having been evaporated  D)being evaporated

5. A) run down             B) run away                         C) run off                     D) run through

6. A) of                        B) with                                C) through             D) from

7. A) upset                    B) created                            C) discovered        D) invented

8. A) only before           B) unless                             C) although            D) only if

9. A) by                        B) for                                  C) over                 D) against

10. A) accord                B) concern                          C) interfere            D) interrupt

11. A) to be understood  B) understanding                  C) to understand    D)being understood

12. A) separate              B) clean                               C) mix                  D) filter

13. A) There are            B) They are                         C) These are          D) Those are

14. A) To start with              B) To name just a few           C) For example      D) In contrast

15. A) produces            B) serves                             C) maintains          D) keeps

16. A) forbids               B) discourages                            C) prevents            D) allows

17. A) there                  B) where                             C) which               D) what

18. A) basis                  B) base                                C) basic                D) basements

19. A) come up with      B) fill up with                       C) disagree with    D) finish with

20. A) dry                     B) snowy                                   C) rainy                 D) misty