While analyzing a company's security solution, a Security Engineer wants to secure the AWS account root user. What should the Security Engineer do to provide the highest level of security for the account?

A. Create a new IAM user that has administrator permissions in the AWS account. Delete the password for the AWS account root user.
B. Create a new IAM user that has administrator permissions in the AWS account. Modify the permissions for the existing IAM users.
C. Replace the access key for the AWS account root user. Delete the password for the AWS account root user.
D. Create a new IAM user that has administrator permissions in the AWS account. Enable multi-factor authentication for the AWS account root user.