The artificial activity that an activity following it, can't start unless the preceding activity is complete, known as A.event B.free float C.dummy

Its a dummy activitty. The answer is C

The definition is "logic dummy" activity, however there is a slight improvement in the definition.

Logic dummies in CPM serve to represent the logic sequencing connection between a prior set of activity and a following activity, the latter which does not require100% but only some of preceding activities to be completed in order to start. It is normally shown in broken lines.

In short there a logic sequencing between the activities but the latter is not100% dependent from the former.

it was introduce to preserve the integrity of the logic sequencing and to avoid contamination of the critical path.

My answer is option (C) Dummy

C >>>>>>>>>>>>>>>>>>>>>>> dummy