An SSL VPN can be used in conjunction with IBM Tivoli Access Manager for Enterprise Single Sign-On to provide remote access to business critical information. Which statement is true about the Mobile ActiveCode （MAC） when it is used with a VPN Solution for remote access？（）

• A、The MAC can only be delivered to a mobile phone and is good for a single use only.
• B、The MAC can be delivered by mobile phone， e-mail， or fax， and it is good for one time authentication only.
• C、The MAC can only be delivered to a mobile phone and it is good until the expiration time is reached， as set by an administrator.
• D、The MAC can be delivered by mobile phone， email， or fax， and it is good until the expiration time is reached， as set by an administrator.