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.