Answer:
during adulthood the proportion of slow-wave sleep gradually declines
Step-by-step explanation:
Slow-wave sleep: the term "slow-wave sleep" is also denoted as SWS, and is determined as an individual's phase-three sleep that is considered as the "deepest phase" of NREM (non-rapid eye movement) sleep and is therefore distinguished through "delta waves" which is being measured by EEG. During this phase of sleep, sleepwalking and dreaming can happen and is often considered as an important part of "memory consolidation".
In the question above, the given statement states that the difference in the sleep patterns of Charlene and her elderly aunt can be best explained via research that explains that during the adulthood proportion of an individual's life the "slow-wave sleep" tends to decline gradually.