Correct Answer - Option 2 : Awaiting for the arrival concrete materials
Dummy activity: It is an activity which has zero duration and is created for the sole purpose of establishing the relationship between two activities. It is represented by dashed lines.
Excavate the foundations: This will be an internal activity (a part of project which requires some duration and cost as well to reach the tail event.
Waiting for the arrival concrete materials: It won’t require any cost nor any time hence it can be called as a dummy activity.
Lay the foundation concrete: This is the second stage after the excavation which will require money and time hence not a dummy activity
Cure the foundation concrete: This is the third stage after the lay of concrete which requires minimum 7 days of curing and manpower & resource cost.