题目内容：
回答（48）题
A．The delta rhythm will disappear，to be replaced by the activity pattern of brain waves． B．If you are an average sleeper，your sleep cycle is as follows．
C．In stage 4 sleep people tend to dream．
D．The lower your stage of sleep，the slower your brain waves will be．
E．This period of rapid eye movement lasts for some 8 to 1 5 minutes and is called REM sleep．
F．This is called stage l sleep．
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