题目内容：

With time flying, people become aged. Then many people even in their middle age often start to notice that their memory and mental clarity are not what they used to be. We suddenly can’t remember      we put the keys just a moment ago, or an old friend’s name, or the name of an old band we used to love. As the brain      , we refer to these occurrences as "senior moments".        seemingly innocent, this loss of mental focus can potentially have a(n)       effect on our  social and        well-being.

Neuroscientists,experts who study the nervous system, are increasingly showing that there’s actually a lot that can be done. It        out that the brain needs exercise in much the same way our muscles do, and the right mental      can significantly improve our basic cognitive(认知)       . Thinking is basically a        of making connections in the brain. To a certain extent, our ability to        in making the connections that drive intelligence is inherited(继承).          , because these connections are made through effort and practice, scientists believe that intelligence can expand and wave      mental effort.

Now, a new Web-based company has taken a step          and developed the first "brain training program" designed to actually help people improve and        their mental sharpness.

The Web-based program       you to systematically improve your memory and attention skills. The program keeps a(n)       of your progress and provides detailed feedback(反馈)       your performance and improvement. Most importantly, it         changes and improves the games you play to         up the strengths you are developing-much like a(n)        exercise routine which requires you to increase resistance and vary your muscle use.

1.A. where          B. when     C. that    D. why

2.A. improves        B. fades            C. recovers      D. falls

3.A. If              B. Unless           C. Once           D. While

4.A. irregular        B. limited          C. damaging        D. positive

5.A. personal         B. psychological    C. mental   D. physical

6.A. turns            B. finds            C. points          D. figures

7.A. connection       B. responses        C. workouts        D. associations

8.A. style            B. functions         C. circumstances    D. atmosphere

9.A. steps            B. condition        C. consequences    D. process

10.A. insist           B. believe    C. succeed   D. fail

11.A. Therefore       B. Moreover       C. Otherwise       D. However

12.A. according to     B. regardless of  C. apart from    D. instead of

13.A. back           B. further    C. aside    D. around

14.A. regain         B. reflect     C. review     D. respond

15.A. suggests        B. makes         C. hurries          D. allows

16.A. hold           B. record          C. order            D. pace

17.A. to             B. with           C. for              D. about

18.A. irregularly      B. habitually        C. constantly        D. unusually

19.A. carry          B. put              C. build            D. take

20.A. risky          B. effective          C. meaningless     D. familiar