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 contains an exchange server 2010 hub transport server named -ex20.you have received instructions from the cio to make sure that - ex20 can receive e-mail messages residing from their clients on the internet. What should you do？（）

• A、you should consider enabling， anonymous users permission group for the client -ex20 receive connector.
• B、You should consider setting up a Receive connector and set the use to Client. Thereafter you should change the port for the connector.
• C、You should consider setting up a Receive connector and set the use to Custom. Thereafter you should change the remote IP addresses range for the connector.
• D、you should consider enabling， anonymous users permission group for the default -ex20 receive connector.