题目内容：
根据下面资料，回答题 As many people hit middle age, they often start to notice that their memoryand mental clarity are not what they used to be. We suddenly can't remember 1 we put the keys just a moment ago, or an old acquaintance's name, or thename of an old band we used to love. As the brain 2 , we refer to theseoccurrences as "senior moments." 3 seemingly innocent, this loss of mentalfocus can potentially have a(n) 4 impact on our professional, social, andpersonal 5
Neuroscientists, experts who study the nervous system, are increasinglyshowing that there's actually a lot that can be done. It 6 out that the brainneeds exercise in much the same way our muscles do, and the right mental 7 can significantly improve our basic cognitive 8 . Thinking isessentially a 9 of making connections in the brain. To a certain extent, ourability to 10 in making the connections that drive intelligence is inherited. 11 , because these connections are made through effort and practice,scientists believe that intelligence can expand and fluctuate 12 mentaleffort.
Now, a new Web-based company has taken it a step 13 anddeveloped the first "brain training program" designed to actually help peopleimprove and regain their mental 14
The Web-based program 15 you to systematically improve yourmemory and attention skills. The program keeps 16 of your progress andprovides detailed feedback 17 your performance and improvement. Mostimportantly, it 18 modifies and enhances the games you play to 19 onthe strengths you are developing - much like a(n) 20 exercise routinerequires you to increase resistance and vary your muscle use.
第（1）题选 A．that
A．that
B．when
B．when
C．why
C．why
D．where
D．where
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答案解析：