Quiz: Bridge Detection Condition

In Tarjan's bridge algorithm, edge $(u, v)$ where $u$ is the DFS parent of $v$ is a bridge when which condition holds?

1. A.low[v] < disc[u]
2. B.low[v] == disc[v]
3. C.low[v] > disc[u]
4. D.low[v] == disc[u]