Of the following differences between the activity$-$on$-$node diagramming method and the activity$-$on$-$arrow diagramming method, which is the most accurate? Question $21$Answer a$.$ The activity$-$on$-$arrow method is always used with project scheduling software and the activity$-$on$-$node method is manual. b$.$ The activity$-$on$-$arrow method may only have one predecessor type and the activity$-$on$-$node method may have four predecessor types. c$.$ The activity$-$on$-$arrow method is more modern than the activity$-$on$-$node method. d$.$ The activity$-$on$-$arrow and activity$-$on$-$node are same. e$.$ The activity$-$on$-$arrow method is a precedence diagramming method, and the activity$-$on$-$node method is not.