In what way does free float differ from total float ？（）
A．Free float is the amount of total float that does not affect the end date, whereas total float is the accumulated amount of free float.
B．There is no difference-the two terms are functionally equivalent.
C．Free float is the amount of time that a schedule activity can be delayed without delaying the early start of any immediately following schedule activities, whereas total float is concerned with delays that do not affect the project finish date.
D．An activity's free float is calculated by subtracting its total float from the critical path's total float.
参考答案：C
解析：
自由时差与总时差的区别是
A) 自由时差是不影响结束日期的总时差, 总时差是自由时差的总和。
B) 毫无区别, 作用一致。
C) 自由时差是一个进度活动在不影响其后活动最早开始的情况下可以延迟的时间, 而总时差是在不影响项目结束日期的情况下可以延迟的时间。
D) 一个活动的自由时差可以从关键路径的总时差减去其总时差计算出来。
自由时差与总时差的区别：自由时差指某个活动在不影响其任何后续活动最早开始时间的情况下可以延迟的时问幅度；总时差指在不影响项目结束时间的情况下可以延迟的时间幅度，通常总时差针对路径而言，被某个路径所共享。时差的另一种英文写法：slack。