Quiz: DP on DAGs

You want the longest path from node $1$ to node $n$ in a DAG with $V$ nodes and $E$ edges. You process nodes in topological order and relax edges. What is the time complexity?

1. A.$O(V!)$ because you consider all permutations
2. B.$O(V \cdot E)$ because you relax all edges for each node
3. C.$O(V^2)$ because you compare all pairs
4. D.$O(V + E)$ because each node and edge is processed once