Final answer:
The most commonly used type of relationship in the Precedence Diagramming Method (PDM) is finish-to-start.
Step-by-step explanation:
In the Precedence Diagramming Method (PDM) used in project management, the finish-to-start relationship is the most commonly used type of relationship. This means that a successor activity cannot start until its predecessor activity has finished.
For example, if you're planning a construction project, you cannot start building the second floor until the first floor has been completed. The finish-to-start relationship is represented by an arrow that starts at the end of the predecessor activity and ends at the start of the successor activity.
Other types of relationships in PDM include start-to-start, finish-to-finish, and start-to-finish. Each of these relationships represents different dependencies between activities in a project.