In the network shown below; activity 4-5 can be started only when -

Concept:

Network Rules:

• Activity is denoted by arrow and even is denoted by node.
• An event does not consume any time or resources.
• A network will have only one initial node, the initial node will have only outgoing arrows.
• A network can have only one final node, the final node will have only incoming arrows.
• An event can not occur until all the activities leading to it are completed.
• No activity can start until its tail event has occurred.
• No event can occur twice. Therefore network looping is not permitted.

Explanation:

In the given network diagram activity 4-5 can be started only when activity 2-4 and activity 3-4 both are completed.

Hence option (3) is correct.