Which XSL if statement checks for the existence of a homepage attribute within an STS Universal User XML structure?（）

A.<xsl:if test="//stsuuser:AttributeList/stsuuser:Attribute[attr='homepage']">
B.<xsl:if test="//stsuuser:AttributeList/stsuuser:Attribute[@name='homepage']">
C.<xsl:if-exists="//stsuuser:AttributeList/stsuuser:Attribute/custom:Homepage">
D.<xsl:if-exists="//stsuuser:AttributeList/stsuuser:Attribute[@name='homepage'])>