Explanation:

The critical path is the longest path in a PERT/CPM chart that determines the minimum time required to complete a project. It consists of a series of interconnected activities or events.

Definition of Slack:

Slack refers to the amount of time that an activity can be delayed without delaying the entire project. It is calculated by finding the difference between the late start time and the early start time of an activity.

Importance of Slack:

Slack helps in identifying the flexibility of activities within a project schedule. It allows project managers to prioritize tasks and allocate resources accordingly. Activities with zero slack are considered critical as any delay in these activities will directly impact the project completion time.

Obtaining Critical Path:

To obtain the critical path on a PERT/CPM chart, we need to identify the activities that have zero slack. These activities are the ones that determine the minimum time required to complete the project.

Explanation of Options:

a) Maximum Slack: If we join the events with maximum slack, it would result in the longest path, not the critical path. This path would not represent the minimum time required to complete the project.

b) Minimum Slack: If we join the events with minimum slack, it would result in a path that includes activities with the least amount of flexibility. While these activities are important, they may not necessarily be part of the critical path.

c) Average Slack: Taking the average slack value would not provide an accurate representation of the critical path. It may include activities with both positive and negative slack, leading to an incorrect path.

d) No Slack: Joining the events with no slack is the correct approach to obtain the critical path. Since these activities have zero slack, any delay in them would directly impact the project completion time. Thus, the critical path is obtained by joining the events with no slack.

Therefore, the correct answer is option 'd' - No slack.