Your Web site processes book orders. One of the application methods contains the following code segment.Dim doc As New XmlDocument（　）doc.LoadXml("10" &_"")You need to remove the discount element from XmlDocument. Which two code segments can you use to achieve this goal? （）

• A、Dim root As XmlNode = doc.DocumentElementroot.RemoveChild(root.FirstChild)
• B、Dim root As XmlNode = doc.DocumentElementroot.RemoveChild(root.SelectSingleNode("discount"))
• C、doc.RemoveChild(doc.FirstChild)
• D、doc.DocumentElement.RemoveChild(doc.FirstChild)