SOX is an alternative（1）for XML. It is useful for reading and creating XML content in a（2）editor. It is then easily transformed into proper XML. SOX was created because developers can spend a great deal of time with raw XML. For many of us, the popular XML（3）have not reached a point where their tree views, tables and forms can completely substitute for the underlying（4）language. This is not surprising when one considers that developers still use a text view, albeit enhanced, for editing other languages such as Java. SOX uses（5）to represent the structure ofan XML document, which eliminates the need for closing tags and a number of quoting devices. The result is surprisingly clear.空白（4）处应选择（）

A. programming
B. command
C. markup
D. interactive