裂隙灯观察视焦点至物镜边缘的连线与主光轴的夹角称（）。

A、固定角

B、孔径角

C、视野角

D、观察角

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．

（75）处填（）。

A．tell

B．know

C．communicate

D．feedback