Given the following information for an AOA network:

Immediate

Activity

Duration $($days$)$

Predecessor$($s$)$

A

$4$

none

B

$2$

A

C

$7$

none

D

$4$

A

E

$5$

$B,C,D$

How many critical activities are there in this AOA network?

Keep your own AOA graph.

Select one:

a$.$ two critical activities

b$.$ four critical activities

c$.$ three critical activities

d$.$ five critical activities