【单选题】Different Stages of Sleep A scientist who has spent many years studying sleep was asked this question: 'Why do we need sleep?' His answer was.'If we do not sleep, we get very sleepy, 'No one knows exa...
【单选题】听力原文:M: Do you have any idea where Samuel is now? It's already 10: 30. This is the third time this week he's not on time. Didn't I make it clear that all waiters and waitresses must be at work by 10, ...