(Quiz week 3, sep 1st) Consider the Activity Time Diagram defined below. The lines, $a$ to $e$, represent the nodes of the Network. The columns, $1$ to $10$, represent the $starging$ and $ending \ times$ of the nodes during a given DFS Algorithm running, which starts at node $a$ and follows alphabetical order through the Network. So, the horizontal bar at row $a$, indicates that node $a$ has $starting \ time = 1$ and $end ending \ time = 10$, delimiting the time it is active, and so on for the others.

Based on info of the diagram, we are able to infer some of the edges characteristics. Then, considering the definitions about Edge Classification, analyze the following statements:

1. Edges $d$ $\rightarrow$ $c$ and $e$ $\rightarrow$ $d$ are cross-edges.
2. Edges $a$ $\rightarrow$ $c$ and $a$ $\rightarrow$ $e$ are forward-edges.
3. Edge $c$ $\rightarrow$ $a$ is a backward-edge.

Given the statements, which of them are true:

1. I and II.
2. I and III.
3. II and III.
4. I, II and III.
5. None of the above.

Original idea by: Fábio Assunção.