Dummy activities A. are found in both AOA and AON networks. B. are used when two activities have identical starting and ending events. C. cannot be on the critical path. D. have a duration equal to the shortest non-dummy activity in the network.

B. are used when two activities have identical starting and ending events.

Explanation:

Dummy activities are used when we want to demonstratethe relationship between two methods or evens, which place option B as the correct one.

Dummy activities have no duration at all, actually they are not suppose to be on the critical path, because they are just demonstrative, so option D and C are not correct.

B. are used when two activities have identical starting and ending events.

Explanation:

A dummy activity is a simulated activity of sorts, one that is of a zero duration and is created for the sole purpose of demonstrating a specific relationship and path of action on the arrow diagramming method. Dummy activities are a useful tool to implement when the specific logical relationship between two particular activities on the arrow diagramming method cannot specifically be linked or conceptualized through simple use of arrows going from one activity to another.