In a Study, Subjects Either Stayed Awake or Went to Sleep

In a study, subjects either stayed awake or went to sleep immediately after memorizing a list of nonsense syllables. From what you've learned in your text, you would expect results to show that forgetting was

A) more rapid when subjects went to sleep.
B) equal whether subjects were asleep or awake.
C) significantly slower when subjects stayed awake.
D) more rapid when subjects stayed awake