这个题考察的是对后面几段的归纳。首先在第三段开始“Dr．Maquet used all electronic device called PET．．．they practiced a task during the day，and as they slept during the following night．”这是一种对比性的研究方法。后来的第四段最后“…their response times when they woke up were even quicker than when they went to sleep．”也采用了对比的分析研究，故应选C。