To solve this question, the user needs to know the basics of XPath and its path expressions.
Now, let's go through each option and explain why it is right or wrong:
A. //: This is a valid XPath path expression which selects all the nodes with the matching name, regardless of their position in the document.
B. @: This is a valid XPath path expression which selects attributes of the selected element.
C. $: This is not a valid XPath path expression. XPath doesn't use $ to select nodes or attributes.
D. /: This is a valid XPath path expression which selects the root node of the document or the current node if used at the beginning of the expression.