— How is that, Mary?

— I wonder ________ it takes to be a good teacher beyond patience and a great knowledge of kids. [      ]

A. how is it that  

B. what it is that

C. how it is that  

D. what is it that

下列指标中（）不是CD-ROM的主要性能指标.

A.容量

B.体积

C.存取时间

D.转速