Which of the Following Is Not One of the Network

Which of the following is not one of the network rules for PERT/CPM?

A) Networks can start and finish at multiple events.
B) Identify each unique activity within a project by a capital letter that corresponds only to that activity.
C) Branch direction indicates the general progression in time from left to right.
D) When a number of activities end at one event, no activity starting at that event may begin before all activities ending at that event are complete.
E) Two or more activities cannot share graphically the same beginning and ending events.