Final answer:
When awakened during REM sleep, 80-90% of people report that they have been dreaming. REM sleep is characterized by brain wave patterns similar to those during wakefulness and is commonly associated with dreams.
Step-by-step explanation:
Regarding the percentage of people who report dreaming when awakened during REM sleep, the correct answer is a. 80-90%. This high percentage reflects the close association between REM sleep and dreaming. REM, which stands for rapid eye movement, is the sleep stage characterized by brain activities similar to those during wakefulness as seen in EEG recordings, which is also typically when vivid dreams occur. People awakened during this sleep stage are more likely to remember their dreams. It's important to note that sleep is divided into several stages, including non-REM and REM sleep, with REM being the one most commonly associated with dream activity.
Sleep spindles and K-complexes, which are distinctive wave patterns on an EEG, are most often associated with option b. stage 2 of non-REM sleep. This stage serves as a transition period between light sleep and very deep sleep.