$12.$ Which of the following is NOT a characteristic of an activity? a$)$ It is a distinct, scheduled portion of work performed during a project b$)$ It has clear starting and ending points c$)$ It is defined using a verb $/$ noun format d$)$ It is one of the deliverables at the lowest level of the WBS Another term for "activity on node," the most commonly used echnique for constructing a schedule model, is:

a$.$ Precedence diagramming method $($PDM$).$

b$.$ Arrow diagramming method $($ADM$).$

c$.$ Activity on arrow $($AOA$).$

d$.$ Activity attribute method $($AAM$).$