A project scheduled to meet a target date was delayed by an unforeseen risk event. How should the project manager compress the schedule so the completion date is not affected?

Fast-tracking is a schedule compression technique where activities that would normally be done in sequence are performed in parallel or with some overlap. This allows the project to potentially finish sooner without changing the project scope. Adding more project resources (crashing) is another compression technique, but it typically increases project cost. Reducing project scope would change the deliverables and might not be acceptable. Increasing project cost is a consequence of some compression techniques, not a technique itself for compressing the schedule.