EXERCISE 24

     Man has been storing up useful knowledge about himself and the universe at the rate which has been spiraling upward for 10000 years.    

     The __1_ took a sharp upward leap with the invention of writing,but even __2_ it remained painfully slow for several centuries.The next great leap forward __3_ knowledge acquisition did not occur __4_ the invention of movable type in the 15th century by Gutenberg and others.__5_ to 1500,by the most optimistic __6_,Europ was producing books at a rate of 1000 titles per year.This means that it __7_ a full century to produce a library of 100000 titles.By 1950,four and a half __8_later,the rate had accelerated so sharply that Europe was producing 120000 ttitles a year._9_ once  took a century now took only ten months.By 1960,a __10_ decade later,the rate had made another significant jump,__11_ a century's work could be finished in seven and a half months.__12_,by the mid-sixties,the output of books on a world__13_,Europe included,approached the prodigious figure of 900 titles per day. 

     One can __14_ argue that every book is a net gain for the advancement of knowledge.Nevertheless we find that the accelerative __15_ in book publication does,in fact,crudely __16_ the rate at which man discovered new knowledge.For example,prior to Gutenberg __17_ 11 chemical elements were known.Antimony the 12th,was discovered __18_ the time he was working on his invention.It was fully 200 years since the 11th,arsenic,had been discovered.__19_ the same rate of discovery contioned,we could by now have added only two or three additional elements to the periodic table since Gutenberg.__20_,in the 450 years after the time,certain people discovered some seventy additional elements.And since 1900 we have been isolating the remaining elements not a rate of one every two centuries,but of one every three years.

1)    A accumulation     B development     C knowledge    D rate

2)    A  so             B if              C then         D when

3)    A  to             B by             C from         D in

4)    A  until           B since           C when        D before

5)    A  as             B due            C prior         D next

6)    A  examples       B estimates        C evidence     D evaluation

7)   A  would take       B had taken      C was taking   D would have taken

8)    A  decades        B centuries        C dozens      D years

9)    A  this            B these          C it           D what

10)   A  plain           B historic        C single       D eventful

11)   A  now that        B so that         C as          D when

12)   A  however       B but             C and        D therefore

13)   A  scope         B sphere          C scale        D stretch

14)  A  therefore       B hardly          C accordingly   D therefore

15)   A  line          B circle           C diagram      D curve

16)   A  fit           B like            C resemble      D parallel

17)   A  about        B only            C more than     D less than

18)   A  in           B at              C on           D for

19)   A  as           B had             C if           D with

20)  A  in addition     B in turn          C instead       D in particular

参考答案:

1--5   DAAAC     6--10   BABDC     11--15  BCCBD     16--20  DBBBC