TOEFL Listening: TPO-TOEFL阅读TPO - 001J9F43R06REG4DN$

Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. Because breathing is more shallow and irregular in REM than in NREM, less air is exchanged in REM. B. Breathing in NREM is less effective than breathing in REM because of irregular episodes of rapid breathing during NREM. C. Because breathing is more rapid in NREM sleep than in REM sleep, breathing often becomes shallow. D. Although REM has brief episodes of shallow breathing or lack of breathing, breathing is more rapid than in NREM.