东北地区的中学生寒假时间很长，主要原因是[ ]

A、这里冬季寒冷漫长

B、学生喜欢放长假

C、寒假时间长是为了充分休息，有利于健康

D、当地政府制定的，为了让学生好好过年

Extreme Programming(XP)is a discipline of software development with (71) of simplicity, communication，feedback and courage．Successful software development is a team effort-not just the development team，but the larger team consisting of customer, management and developers．XP is a simple process that brings these people together and helps them to succeed together．XP is aimed primarily at object-oriented projects using teams of a dozen or fewer programmers in one location．The principles of XP apply to any (72) project that needs to deliver quality software rapidly and flexibly． An XP project needs a (73) customer to provide guidance．Customers，programmers, managers，are all working (74) to build the system that’s needed．Customers-those who have software that needs to be developed-will learn simple, effective ways to (75) what they need，to be sure that they are getting what they need，and to steer the project to success.

73（）

A．part-time

B．casual

C．seldom

D．full-time