Events vs activities in network planning Which of the following best represents an event (i.e., a zero-duration milestone state) rather than an activity?

Introduction / Context:
In PERT/CPM networks, an activity consumes time and resources, while an event (milestone) is an instant in time marking the start or completion of one or more activities. Distinguishing between them is crucial for correct modeling.

Given Data / Assumptions:

• Activities like fixing doors or plastering require time.
• Events capture states achieved, such as 'concrete cured' once curing duration is complete.

Concept / Approach:
Represent actions requiring time as activities; represent achieved conditions with zero duration as events. The event symbolizes completion of predecessor activities and the readiness to start successors.

Step-by-Step Solution:
Identify time-consuming tasks: fixing doors, plastering, and site selection are activities.Identify a milestone/condition: 'concrete cured' is a state that is attained at an instant (after curing time has elapsed).Therefore, 'Concrete cured' is the event.

Verification / Alternative check:
Draw a small network: an activity 'Cure concrete' precedes an event 'Concrete cured'; successors (e.g., load testing) can start from that event.

Why Other Options Are Wrong:
They describe activities (doing work) rather than milestone states; each has non-zero duration and resource usage.

Common Pitfalls:
Labeling actions as events; remember that events are zero duration checkpoints while tasks are modeled as activities.

Final Answer:
Concrete cured