What Is the Slack Time for Activity D Given the Activity

What is the slack time for Activity D given the activity times and precedence requirements shown in the table? $$\begin{array} { | l | l | l | } \hline \text { Activity } & \text { Time } & \text { Predecessor } \\\hline \mathrm { A } & 5 & - - \\\hline \mathrm {B} & 7 &- - \\\hline \mathrm { C } & 8 & \text { A } \\\hline \mathrm { D } & 7 & \mathrm {~A} \\\hline \mathrm { E } & 4 & \mathrm {~B} \\\hline \mathrm { F } & 8 & \mathrm { C } , \mathrm { D } \\\hline \mathrm { G } & 9 & \mathrm { E } , \mathrm { F } \\\hline \mathrm { H } & 7 & \mathrm { G } \\\hline\end{array}$$

A) 2
B) 1
C) 0
D) 3