Which of the following statement is true? Question 19Select one: a. To reduce a project's duration, activities with positive slack must be crashed. b. If each of the two consecutive activities on the same path has two days of activity slack, then each of them can be delayed by two days without delaying the project. c. The standard deviation of the critical path is equal to the sum of the standard deviations of all of the activities on the critical path. d. A document that provides a common understanding and justification for a project is known as a work breakdown structure. e. The use of a network to depict precedence relationships between activities is an advantage of CPM/PERT over the Gantt chart