In PERT (Program Evaluation and Review Technique), which of the following is a valid event representation?

Introduction / Context:
PERT is a probabilistic network method emphasizing events (milestones) and activities for planning and control of projects under uncertainty. Understanding what constitutes an event is crucial for constructing correct networks and identifying critical milestones.

Given Data / Assumptions:

• We must choose which statements are legitimate events.
• Options include start and completion of specific construction tasks.
• Event in PERT is a point in time signifying the start or finish of an activity.

Concept / Approach:
An event is instantaneous (no duration) and marks the occurrence of a significant point such as the start or finish of an activity. Therefore, statements indicating “started” or “completed” are valid events.

Step-by-Step Solution:
Step 1: Identify the definition of an event: zero-duration milestone.Step 2: Check each option: “started” and “completed” both denote milestones.Step 3: Since all listed milestones are valid, select the comprehensive option.

Verification / Alternative check:
PERT/CPM references consistently define events as the start or finish of activities; all given statements fit this definition.

Why Other Options Are Wrong:

• Individual start/finish choices are correct but incomplete.
• Only “All the above.” captures the full set of valid events.

Common Pitfalls:
Confusing activities (which have duration) with events (which do not), or assuming only “completion” qualifies as an event.

Final Answer:
All the above.