问题
单项选择题
You will fall into the fourth stage of sleep ______.
A．about 80 minutes after you fall into slumber
B．some 10 minutes after your fall into REM sleep
C．about 40 minutes after you lose consciousness
D．some 30 minutes after your brain waves slow
答案
参考答案：C
解析：[分析] 细节题型。 根据第一段第六句About 40-60 minutes after you lose consciousness, you will reach the last stage．得知答案。