题目内容：
回答题：Documentation of a software package is normally produced for two purposes. One is to explain the __(71)__ of the software and describe how to use them. This is known as __(72)__ because it is designed to be read by the user of the software. The other purpose of documentation is to describe the software’s internal composition so that the system can be maintained later in its life cycle. Documentation of this type is known as __(73)__.（71）空正确答案是： A．plans
B．cost
C．features
D．schedules
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