Was it through Li Ning, ______ working at a high school, ______ you got to know Wangke? [ ]

A. who I think it was; who

B. that I think were; which

C. who I think was; that

D. I think who was; which

下列4项中，可以直接用于表示概念模型的是( )。

A．实体-联系(E-模型

B．关系模型

C．层次模型

D．网状模型