在水泥土搅拌桩中可掺入哪些外加剂，这些外加剂的作用是什么？

The expected time TE used in the PERT algorithm is calculated using the following equation ______.

A) (a+3m+b)/6
B) (a+4m+b))/6
C) (a+5m+b)/6
D) (a+m+b)/3
Note: A major assumption for all network methods is that activity durations are statistically dependent and where a=most optimistic time, b=most pessimistic time, m=most likely time.