You are implementing an ASP.NET Web site. The site contains the following class.  The Web site interacts with an external data service that requires Address instances to be given in the following XML format. You need to ensure that Address instances that are serialized by the XmlSerializer class meet the XML format requirements of the external data service. Which two actions should you perform.（）

• A、Add the following attribute to the AddressType field. [XmlAttribute]
• B、Add the following attribute to the Line2 field. [XmlElement（IsNullable=true）]
• C、Add the following attribute to the ZipPostalCode field. [XmlAttribute（"ZipCode"）]
• D、Add the following attribute to the ZipPostalCode field. [XmlElement（"ZipCode"）]