The following table represents a small business project with known activity times for an AOA network:

$\backslash$table$[[$Activity$,$Immediate Predecessor$($s$),$Time Duration $($days$)],[$A$,$None,$4],[$B$,$None,$3],[$C$,$A$,2],[$D$,$B$,7],[$E$,$C$,$D$,5],[$F$,$B$,5]]$

How many critical activity $($activities$)$ is $($are$)$ there in this AOA network?

Keep your own AOA graph.

Select one:

a$.2$ critical activities

b$.1$ critical activity

c$.3$ critical activities

d$.5$ critical activities

e$.4$ critical activities