The program evaluation and review technique (PERT) is . a. a network-based technique in which there is a single time estimate for each activity b. a network-based technique in which there are multiple time estimates for each activity c. a graphical tool that shows the logical linkages between activities in a project d. a graphical tool used to show expected start and end times for project activities and to track actual progress against these time targets e. I DON'T KNOW YET