You need to design a strategy for providing e-mail access to the subsidiary users. What should you do？（）

• A、Deploy POP3 and IMAP4 services on Exchange front-end servers. Make the front-end servers accessible from the Internet by means of POP3， IMAP4， and SMTP only
• B、Deploy Microsoft Outlook Web Access on Exchange mailbox servers. Make the mailbox servers accessible from the Internet by means of HTTPS and SMTP only
• C、Deploy Microsoft Outlook Web Access on Exchange front-end servers. Make the front-end servers accessible from the Internet by means of HTTPS only
• D、Deploy an additional Exchange mailbox server that contains all subsidiary mailboxes. Deploy Microsoft Outlook Web Access on the server. Make the server accessible from the Internet by means of HTTPS only