A company secures its AWS account root user with a multi-factor authentication (MFA) device and wants to ensure it will not lose access to the root user if the MFA device is lost. Which solution meets this requirement?

Adding multiple MFA devices to the root user account is the correct solution. AWS allows you to register up to eight MFA devices for the root user. If one device is lost or inaccessible, the company can use another registered MFA device to authenticate and regain access, preventing a lockout. Setting up a backup administrator account is incorrect because the root user is unique and has permissions that cannot be fully replicated by an IAM user, even an administrator. Creating a new administrator account or attaching an administrator policy to another IAM user when the root account is inaccessible is not possible without root or an existing administrator's credentials, which would be the problem if the MFA device for the root user is lost.