A simple CPM network has three activities, A$,$ B$,$ and C$.$ A is an immediate predecessor of $B$ and of $C.B$ is an immediate predecessor of $C.$ The activity durations are $A=5,B=7,C=6.$

The network has no critical path.

The critical path is A$-$C$,$ duration $11.$

The critical path is A$-$B$-$C$,$ duration $18.$

The critical path cannot be determined without knowing PERT expected activity times.

The critical path is $A-B,$ duration $12.$