The correct option is ReadWriteOnce.

ReadWriteOnce means the Persistent Volume can be mounted read write by a single node and it prevents concurrent read write mounts from multiple nodes. That fits the requirement of one node having read write access while other nodes must not be able to write at the same time.

Whether additional nodes can also mount the same volume read only depends on the storage backend, but the access mode that enforces single-node write is ReadWriteOnce.

ReadWriteMany is incorrect because that mode allows many nodes to mount the volume read write simultaneously, so it does not restrict write access to a single node.

ReadOnlyMany is incorrect because that mode only allows multiple nodes to mount the volume read only and it cannot provide a read write mount for the single node.

ReadWriteOncePod is incorrect because it is a different mode that constrains write access to a single Pod rather than expressing the node level write restriction described in this question.

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