Enabling "Cluster Lockdown" in Nutanix is the best security measure to prevent password-based SSH logins.

Option C (Enable Cluster Lockdown) is correct:

Cluster Lockdowndisables password-based SSHandrequires key-based authentication.

Option A (Rename the nutanix user) is incorrect:

The Nutanix useris a system accountand cannot be renamed.

Option B (Block port 22) is incorrect:

This wouldprevent all SSH connections, includingkey-based logins, making administration difficult.

Option D (Delete the nutanix user) is incorrect:

Thenutanix useris required for system operations and cannot be removed.