a.

In an activity-on-node network, activities are depicted as arrows and the nodes represent completion of milestone events, while in an activity-on-arrow network, the arrows represent activities and the nodes denote precedence relations between activities.

b.

In an activity-on-node network, activities are depicted as nodes, while in an activity-on-arrow network, the arrows represent activities.

c.

In an activity-on-node network, the arrows denote activities, while in an activity-on-arrow network, the nodes represent completion of milestone events.

d.

In an activity-on-node network, the arrows denote precedence relations between activities, while in an activity-on-arrow network, the nodes represent activities.