A Simple Project Listing of Five Activities,their Predecessors and Their

A simple project listing of five activities,their predecessors and their respective time estimates are presented below: $$\begin{array} { | l | l | l | } \hline \text { Activity } & \text { Immediate Predecessor } & \text { Time in Days } \\\hline \text { A } & \text { None } & 2 \\\hline \text { B } & \text { A } & 2 \\\hline \text { C } & \text { A } & 1 \\\hline \text { D } & \text { B and C } & 3 \\\hline \text { E } & \text { D } & 1 \\\hline\end{array}$$
Using the CPM,which activities have slack in this project?

A) A
B) B
C) C
D) D
E) C and E