试述数据库关系系统三级模式结构,这种结构的优点是什么?
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______ frightened me was a loud crash from the next door.
A. How
B. What
C. That
D. Why
He got a message from Miss Zhang_______ Professor Wang couldn't see him in the following day.
A. which
B. whom
C. that
D. what
_______ we need more practice is quite clear.
A. When
B. What
C. That
D. If
______ I accepte the gift or refuse it is none of your business.
A. If
B. whether
C. When
D. How