What is critical path?

Select one:a. Longest sequence of activities in a project plan with a built-in slack for contingencyb. Shortest sequence of activities in a project plan to complete the project on timec. The critical path is the longest sequence of activities in a project plan which must be completed on time for the project to complete on due date.d. Critical activities with the highest values in a project plane. Shortest sequence of activities in a project plan with a built-in slack for contingency