You work as the enterprise exchange administrator at Company.com.The Company.com network consists of a single Active Directory domain named Company.com.Company.com has an Exchange Server 2010 organization.Company.com makes use of an exchange server 2010 edge transport server named -sr18.You have configured the other exchange server 2003 servers to forward the e-mails for external recipients to -sr18.You have received instructions from the cio to make sure that -sr18 can send and receive e-mail messages from the internet. What should you do？（）

• A、The best option is to set up and configure a sharing policy.
• B、the best option is to set up and configure a send connector on -sr18.thereafter you should set up and configure a receive connector on -sr18.
• C、The best option is to make use of the Exchange Server 2010 schema extensions.
• D、The best option is to set up an Edge Subscription file and duplicate the file to the Exchange Server 2003 servers.