Given the following small project for an AOA network,

$\backslash$table$[[$Activity$,$Immediate Predecessor$($s$),$Time Duration $($days$)],[$A$,$None,$10],[$B$,$None,$2],[$C$,$A$,$ E$,9],[$D$,$None,$3],[$E$,$B$,$ D$,5]]$

How many dummy arc$($s$)$ should be there in this AOA totally?

Select one:

a$.$ one dummy arc

b$.$ two dummy arcs

c$.$ four dummy arcs

d$.$ no dummy arc

e$.$ three dummy arcs