单项选择题
A.单据主键B.管理对象主键C.凭证主键D.任意字符
A.com.ygsoft.ecp.service.storage.pointB.com.ygsoft.ecp.service.attachment.pointC.com.ygsoft.ecp.service.unstructure.pointD.com.ygsoft.ecp.service.file.point
A.EcpServiceB.StorageServiceC.AttachmentServiceD.EntityAttachmentService