XML is a (71) language for documents containing (72) information.
Structured information contains both content(words, pictures, etc.)and some indication of what role that content plays(for example, content in a section heading has a different meaning from content in a footnote, which means something different than content in a figure caption or content in a database table, etc.). Almost all documents have some structure.
A markup language is a (73) to (74) structures in a document. The XML specification defines a standard way to add markup to (75) .
（73）处填（）。
A．algorithm
B．arithmetic
C．mechanism
D．mechanistic
读取水的体积
