When you create a single-node cluster, which statement is correct about the cluster base license
key?

A.
A single-node cluster does not need any cluster-base license key.

B.
A single-node clustered Data ONTAP 8.1 license key is seven characters long.

C.
Clustered Data ONTAP 8.2 and 8.3 license keys are 14 characters long.

D.
A single-node cluster requires a cluster base key to use a cluster.

Explanation:
A Cluster Base Key required to create a Single-Node Cluster.
Incorrect:
Not A: A single-node Cluster requires a Cluster Base Key to run the create cluster command.
Not B: Clustered ONTAP 8.1 license keys are fourteen (14) characters long. FAQ – Data ONTAP Licensing
https://kb.netapp.com/index?page=content&id=3013756&actp=LIST_POPULAR