练习
Ⅰ Cloze
Is there a population problem?
My answer 1 the question is "YES", there is a problem. The scale of human activities is now so __2__ that we are appreciably 3 the climate and ecosystems in the U.S. and the world.
The total impact of people __4__ the environment is proportional __5__ each of two factors:
A) The number of people, and
B) The _6___ impact of each person.
If we are to_ 7___ the total impact of people on the global environment, we must address the first, or preferably both, of these __8__.
There are many strong forces that will cause ___9_ growth of the average impact of each person on the global environment. To the __10__ that people in underdeveloped countries __11_ increase their material standard of living to levels more like ours, material consumption per capita will grow. So we are left __12__ the imperative of halting population growth, and then of __13__ the question, "Can this stable population be sustained?"
To gain a better __14__ of the seriousness of the problem, let us review some very elementary __15__. Let us consider a __16__ that is experiencing steady growth _17___ such as 5% per year.
First we note that this growing quantity will double _18__ in a __19__ time. This _20___ time is found by dividing 70 by the percent growth per year. For example, the doubling time for a steady growth rate of 5% per year is 70 / 5 = 14 years.
Second, we note that a few doublings can give enormous numbers. It is convenient to 20 remember that ten doublings causes the growing quantity to increase in size by a factor of approximately 1000: twenty doublings will cause an increase by a factor of 1,000,000, etc.
1. [A]of [B]to [C]with [D]for
2. [A]large [B]big [C]small [D]little
3. [A]effecting [B]causing [C]affecting [D]affiliating
4. [A]with [B]of [C]to [D]on
5. [A]of [B]to [C]within [D]for
6. [A]average [B]averagenal [C]averaged [D]averaging
7. [A]decrease [B]reduce [C]decline [D]deduce
8. [A]truths [B]facts [C]factors [D]elements
9. [A]continued [B]continuous [C]continual [D]continuity
10. [A]scale [B]extent [C]range [D]sphere
11. [A]seek to [B]seek [C]seek after [D]seek for
12. [A]of [B]by [C]as [D]with
13.[A]learning [B]studying [C]searching [D]researching
14.[A]appreciation [B]understanding [C]awareness [D]knowledge
15.[A]arithmetician [B]arithmetically [C]aristocratic [D]arithmetic
16.[A]amount [B]quality [C]quantity [D]number
17. [A]on