Quiz: Round Trip Pattern

Round Trip: Find a cycle in an undirected graph. During DFS from node $u$, you see neighbor $v$ that's already visited. Is this always a cycle?

1. A.No, only if $v$ is the starting node
2. B.No, only if $v$ is not the parent of $u$
3. C.Yes, but only in directed graphs
4. D.Yes, any visited neighbor means a cycle