In a project network, the artificial activity used solely to show dependency (that a following activity cannot start until a preceding one is complete) is called:

Introduction / Context:
Network techniques (PERT/CPM) sometimes require artificial constructs to express logic without implying real work or time consumption. Understanding these constructs ensures correct dependency modeling.

Given Data / Assumptions:

• The activity in question indicates only precedence, not real work.
• It carries zero duration and zero resource needs.
• Its purpose is to maintain correct logical relationships and network integrity.

Concept / Approach:
A dummy activity is a zero-duration connector used in Activity-on-Arrow (AOA) networks to preserve logic when two activities share some but not all predecessors, or when unique identification of relationships is needed.

Step-by-Step Solution:
Step 1: Differentiate real activities (with duration) from artificial links (no duration).Step 2: Recognize that an “event” is a node (milestone), not an activity.Step 3: Identify “dummy” as the artificial, zero-time activity used to express precedence only.

Verification / Alternative check:
Classic PERT/CPM AOA notation depicts dummy as a dashed arrow with duration = 0 to represent pure dependency.

Why Other Options Are Wrong:

• event: A milestone node, not an activity.
• free float: A scheduling parameter (slack), not an activity.
• constant: Not a standard term in network modeling.

Common Pitfalls:
Assigning time or resources to dummies; confusing dummies with actual work or with float/slack concepts.

Final Answer:
dummy