— I think your father is very busy.

—So he is._______ he still takes a walk with us sometimes.

A. So          B. And        C. Or          d. But

字符流(character stream)是一种( )。

A．特殊类型的字节流，仅仅处理文本数据

B．一种类型的流

C．它修改了处理现存流的方式

D．它可用来处理文件