According to the author of the passage, which of the following generalizations about memory and sleep is true? A. There are some memory-consolidation processes that have nothing to do with sleep. B. Sleep is more important to the consolidation of declarative memory than to the consolidation of other types of memory. C. REM sleep is more important to memory consolidation than is non-REM sleep. D. There are significant variations in the amount of sleep that people require for the successful consolidation of memory. E. It is likely that memory is more thoroughly consolidated during wakefulness than during sleep.