Our teacher told us that _______ moon moves around ______ earth, and

________ earth circles________ sun.

A．a, a, a, a

B．an, an, an, an

C．the, the, the, the

D．/, /, /, /

关系模型中的关系模式至少是( )。

A．1NF

B．2NF

C．3NF

D．4NF