Your Web site processes book orders. One of the application methods contains the following code segment.Dim doc As New XmlDocument()doc.LoadXml("10" &_"Dictionary")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)