What is meant by activity dependencies and how do they relate to network diagramming?

What will be an ideal response?

This is a two part answer. The first part explains what an activity dependency is. For
example, one activity has to be completed before the next can begin, so the second
activity is dependent on the prior. These can be a result of one of three reasons: they are
mandatory, discretionary, or external. The second part is that these dependencies dictate
how activities are both connected and sequenced in a network diagram.