Traditional structured analysis techniques focus upon the flow of （71） within a system. Object-oriented analysis emphasizes the building of real-world models. It examines requirements from the perspective of the classes and objects found in the vocabulary of the （72） domain. Traditional system design method emphasizes the proper and effective structure of a complex system. Object-oriented design method encompasses the process of object-oriented decomposition and a （73） for depicting both logical and physical as well as static and dynamic models of the system under design. Object-oriented programming is a method of implementation in which programs are organized as cooperative collections of objects, each of which represents an （74） of some class, and whose classes are all members of a hierarchy of classes united via （75） relationships.

（73）处填（）。

A．mark

B．picture

C．symbol

D．notation

如图为江阴长江大桥。“桥塔为什么要造这么高？”小强对此进行了研究：他将大桥的结构进行简化，抽象成图乙所示的模型，又画了桥塔高低不同的两幅图丙和丁。小强通过比较发现：适当增加塔的高度，可_______（选填“增大”或“减小”）力臂，从而_________（选填“增大”或“减小”）斜拉索的拉力。