甲、乙两地相距340千米，客、货两辆汽车同时从两地相对开出，4小时后两车相遇。已知客车和货车的速度比是8：9，客车每小时行多少千米？

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.

72（）

A．problem

B．solution

C．data

D．program