B. The administrator must use a FortiAuthenticator device.
B is correct due to the FortiToken, a different OTP cannot use FortiToken. So we have to choose the fortiAuthenticator.
To achieve VPN user access for multiple sites using the same soft FortiToken, the administrator can use a FortiAuthenticator device. FortiAuthenticator is designed to provide centralized authentication services for Fortinet devices, including VPN authentication. It allows for the centralized management of user identities, authentication methods, and FortiTokens. By using FortiAuthenticator, the administrator can register the same FortiToken for users across multiple FortiGate devices, providing a seamless and centralized user access experience.