There are a few ways in Vault that can be used to obtain a root...

Comprehensive and Detailed In-Depth Explanation:

Root tokens are restricted in creation. The Vault documentation states:

"Root tokens are tokens that have the root policy attached to them. In fact, there are only three ways to create root tokens:

The initial root token generated at vault operator init -- this token has no expiration

By using another root token; a root token with an expiration cannot create a root token that never expires

By using vault operator generate-root with the permission of a quorum of unseal/recovery key holders"—Vault Concepts: Tokens

A,B,D: Correct per the above.

C: Incorrect; DR tokens are for replication, not root creation:

"DR operation tokens are typically used for disaster recovery operations and may not be directly related to generating a root token in Vault."

—Vault Replication