Refer to Figure $4.$ Which is not true about the PERT schedule? Select the most appropriate one.

Figure $4$

Activity

$x=$ optimistic duration

$(x,y,z)$

$y=$ most$-$likely duration

$z=$ pessimistic duration

$($A$)$ The standard deviation for Activity C$\text{'}$s duration is $\frac{1}{3}.$

B Activity $B$ has the longest expected duration among the four activities.