Final answer:
The practice of securing a copy of the private keys for all users to ensure recovery of lost keys is known as key escrow.
Step-by-step explanation:
Discovering a folder containing a secured copy of the private key for all users in your organization, and maintaining this copy to ensure the ability to recover lost keys, is an example of a security practice known as key escrow.
Key escrow is a security mechanism in which a third party holds a copy of the encryption keys. This allows organizations to safeguard against the loss of keys by ensuring that there is a way to recover important encrypted data if necessary. It's a common practice for managing cryptographic keys within an enterprise setting to prevent data loss.
The correct answer to the question is: D) key escrow.