Company.com network consists of a single Active Directory domain named Company.com.Company.com has an Exchange Server 2010 organization.the Company.com employees connect to outlook web app （owa） by using https.Company.com also contains a client access server named -ex11 that make use a certificate issued that is acquired by the internal certification authority （ca）.you need to make sure that the employees can use s/mime from owa to send and receive encrypted e-mail messages.What should you do？（）

• A、You should consider changing the OWA virtual directory’s authentication settings.
• B、You should consider issuing the employees a certificate.
• C、You should consider using a third-party ca for -ex11.
• D、You should consider importing a root CA certificate for each employee.