A solutions architect is reviewing the security of an AWS account. The architect notices that the AWS account root user has been used recently to perform administrative tasks. What should the architect recommend to secure the root user? (Select the BEST answer.)

Delete the root user and create an IAM user with AdministratorAccess.

Enable multi-factor authentication (MFA) on the root user, create an IAM admin user for daily tasks, and lock away the root user credentials.

Attach an IAM policy to the root user that denies all actions except billing access.

Generate access keys for the root user and use them in a secure bastion host.