After how long does Kubernetes force-detach a volume from a node where a Pod deletion has not succeeded and the node is unhealthy?

Answer: D. 6 minutes

Six minutes is the threshold, after which the volume is force-detached; because a workload may still be running there, this can corrupt data, which is why the behaviour can be disabled.

Source: Node Shutdowns (Kubernetes) — Non-graceful node shutdown handling › Forced storage detach on timeout