Operating systems .Give answers in detail

1. THE operating systems under goes trades-offs. What are they?
2. How do the requirements of the Pilot operating system differ from the systems we have read about so far, and how does the design of Pilot reflect those differences?
3. Explain the similarities and differences between u-kernel and VM hypervisor?
4. At a high level, lottery scheduling provides modular resource management while UNIX scheduler does not? Why